diff --git a/enumer.go b/enumer.go
index c234209..e553546 100644
--- a/enumer.go
+++ b/enumer.go
@@ -3,6 +3,7 @@ package main
 import "fmt"
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringNameToValueMethod = `// %[1]sString retrieves an enum value from the enum constants string name.
 // Throws an error if the param is not part of the enum.
@@ -19,6 +20,7 @@ func %[1]sString(s string) (%[1]s, error) {
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringValuesMethod = `// %[1]sValues returns all values of the enum
 func %[1]sValues() []%[1]s {
@@ -27,6 +29,7 @@ func %[1]sValues() []%[1]s {
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringsMethod = `// %[1]sStrings returns a slice of all String values of the enum
 func %[1]sStrings() []string {
@@ -37,6 +40,7 @@ func %[1]sStrings() []string {
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringBelongsMethodLoop = `// IsA%[1]s returns "true" if the value is listed in the enum definition. "false" otherwise
 func (i %[1]s) IsA%[1]s() bool {
@@ -50,6 +54,7 @@ func (i %[1]s) IsA%[1]s() bool {
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const stringBelongsMethodSet = `// IsA%[1]s returns "true" if the value is listed in the enum definition. "false" otherwise
 func (i %[1]s) IsA%[1]s() bool {
@@ -59,6 +64,7 @@ func (i %[1]s) IsA%[1]s() bool {
 `
 
 // Arguments to format are:
+//
 //	[1]: type name
 const altStringValuesMethod = `func (%[1]s) Values() []string {
 	return %[1]sStrings()
@@ -144,6 +150,7 @@ func (g *Generator) printNamesSlice(runs [][]Value, typeName string, runsThresho
 }
 
 // Arguments to format are:
+//
 //	[1]: type name
 const jsonMethods = `
 // MarshalJSON implements the json.Marshaler interface for %[1]s
@@ -169,6 +176,7 @@ func (g *Generator) buildJSONMethods(runs [][]Value, typeName string, runsThresh
 }
 
 // Arguments to format are:
+//
 //	[1]: type name
 const textMethods = `
 // MarshalText implements the encoding.TextMarshaler interface for %[1]s
@@ -189,11 +197,12 @@ func (g *Generator) buildTextMethods(runs [][]Value, typeName string, runsThresh
 }
 
 // Arguments to format are:
+//
 //	[1]: type name
 const yamlMethods = `
 // MarshalYAML implements a YAML Marshaler for %[1]s
 func (i %[1]s) MarshalYAML() (interface{}, error) {
-	return i.String(), nil
+	return i.string()
 }
 
 // UnmarshalYAML implements a YAML Unmarshaler for %[1]s
diff --git a/sql.go b/sql.go
index 09f050c..1795316 100644
--- a/sql.go
+++ b/sql.go
@@ -1,9 +1,10 @@
 package main
 
 // Arguments to format are:
+//
 //	[1]: type name
 const valueMethod = `func (i %[1]s) Value() (driver.Value, error) {
-	return i.String(), nil
+	return i.string()
 }
 `
 
diff --git a/stringer.go b/stringer.go
index 49c87fd..0b52ce2 100644
--- a/stringer.go
+++ b/stringer.go
@@ -774,28 +774,40 @@ func (g *Generator) buildOneRun(runs [][]Value, typeName string) {
 }
 
 // Arguments to format are:
-// 	[1]: type name
-// 	[2]: size of index element (8 for uint8 etc.)
-// 	[3]: less than zero check (for signed types)
-const stringOneRun = `func (i %[1]s) String() string {
+//
+//	[1]: type name
+//	[2]: size of index element (8 for uint8 etc.)
+//	[3]: less than zero check (for signed types)
+const stringOneRun = `func (i %[1]s) string() (string, error) {
 	if %[3]si >= %[1]s(len(_%[1]sIndex)-1) {
-		return fmt.Sprintf("%[1]s(%%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _%[1]sName[_%[1]sIndex[i]:_%[1]sIndex[i+1]]
+	return _%[1]sName[_%[1]sIndex[i]:_%[1]sIndex[i+1]], nil
+}
+
+func (i %[1]s) String() string {
+	val, _ := i.string()
+	return val
 }
 `
 
 // Arguments to format are:
-// 	[1]: type name
-// 	[2]: lowest defined value for type, as a string
-// 	[3]: size of index element (8 for uint8 etc.)
-// 	[4]: less than zero check (for signed types)
-const stringOneRunWithOffset = `func (i %[1]s) String() string {
+//
+//	[1]: type name
+//	[2]: lowest defined value for type, as a string
+//	[3]: size of index element (8 for uint8 etc.)
+//	[4]: less than zero check (for signed types)
+const stringOneRunWithOffset = `func(i %[1]s) string() (string, error) {
 	i -= %[2]s
 	if %[4]si >= %[1]s(len(_%[1]sIndex)-1) {
-		return fmt.Sprintf("%[1]s(%%d)", i + %[2]s)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _%[1]sName[_%[1]sIndex[i] : _%[1]sIndex[i+1]]
+	return _%[1]sName[_%[1]sIndex[i] : _%[1]sIndex[i+1]], nil
+}
+
+func (i %[1]s) String() string {
+	val, _ := i.string()
+	return val
 }
 `
 
@@ -820,7 +832,7 @@ func (g *Generator) buildMultipleRuns(runs [][]Value, typeName string) {
 			typeName, i, typeName, i, typeName, i)
 	}
 	g.Printf("\tdefault:\n")
-	g.Printf("\t\treturn fmt.Sprintf(\"%s(%%d)\", i)\n", typeName)
+	g.Printf("\t\treturn \"\"\n")
 	g.Printf("\t}\n")
 	g.Printf("}\n")
 }
@@ -861,10 +873,15 @@ func (g *Generator) buildNoOpOrderChangeDetect(runs [][]Value, typeName string)
 }
 
 // Argument to format is the type name.
-const stringMap = `func (i %[1]s) String() string {
+const stringMap = `func (i %[1]s) string() (string, error) {
 	if str, ok := _%[1]sMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("%[1]s(%%d)", i)
+	return "", fmt.Errorf("value is out of enum range") 
+}
+
+func (i %[1]s) String() string {
+	str, _ := i.string()
+	return str
 }
 `
diff --git a/testdata/day.go b/testdata/day.go
index 106da37..1a59043 100644
--- a/testdata/day.go
+++ b/testdata/day.go
@@ -28,8 +28,8 @@ func main() {
 	ck(Friday, "Friday")
 	ck(Saturday, "Saturday")
 	ck(Sunday, "Sunday")
-	ck(-127, "Day(-127)")
-	ck(127, "Day(127)")
+	ck(-127, "")
+	ck(127, "")
 	ckDayString(Sunday, "Sunday")
 	ckDayString(Sunday, "sunday")
 
diff --git a/testdata/day.golden b/testdata/day.golden
index f23e69b..a79333d 100644
--- a/testdata/day.golden
+++ b/testdata/day.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 6, 13, 22, 30, 36, 44, 50}
 
 const _DayLowerName = "mondaytuesdaywednesdaythursdayfridaysaturdaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 func (Day) Values() []string {
diff --git a/testdata/dayTrimAndPrefix.golden b/testdata/dayTrimAndPrefix.golden
index 7f5367d..3160cab 100644
--- a/testdata/dayTrimAndPrefix.golden
+++ b/testdata/dayTrimAndPrefix.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 11, 23, 37, 50, 61, 74, 85}
 
 const _DayLowerName = "nightmondaynighttuesdaynightwednesdaynightthursdaynightfridaynightsaturdaynightsunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/dayWithLinecomment.golden b/testdata/dayWithLinecomment.golden
index c6b8584..d90b901 100644
--- a/testdata/dayWithLinecomment.golden
+++ b/testdata/dayWithLinecomment.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 5, 12, 21, 29, 36, 44, 50}
 
 const _DayLowerName = "lunestuesdaywednesdaythursdayviernessaturdaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/dayWithPrefix.golden b/testdata/dayWithPrefix.golden
index d468741..8dc17fa 100644
--- a/testdata/dayWithPrefix.golden
+++ b/testdata/dayWithPrefix.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 9, 19, 31, 42, 51, 62, 71}
 
 const _DayLowerName = "daymondaydaytuesdaydaywednesdaydaythursdaydayfridaydaysaturdaydaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/gap.go b/testdata/gap.go
index bc8a90c..f2b6575 100644
--- a/testdata/gap.go
+++ b/testdata/gap.go
@@ -22,19 +22,19 @@ const (
 )
 
 func main() {
-	ck(0, "Gap(0)")
-	ck(1, "Gap(1)")
+	ck(0, "")
+	ck(1, "")
 	ck(Two, "Two")
 	ck(Three, "Three")
-	ck(4, "Gap(4)")
+	ck(4, "")
 	ck(Five, "Five")
 	ck(Six, "Six")
 	ck(Seven, "Seven")
 	ck(Eight, "Eight")
 	ck(Nine, "Nine")
-	ck(10, "Gap(10)")
+	ck(10, "")
 	ck(Eleven, "Eleven")
-	ck(12, "Gap(12)")
+	ck(12, "")
 }
 
 func ck(gap Gap, str string) {
diff --git a/testdata/gap.golden b/testdata/gap.golden
index cc3e48d..6a54c83 100644
--- a/testdata/gap.golden
+++ b/testdata/gap.golden
@@ -25,7 +25,7 @@ func (i Gap) String() string {
 	case i == 11:
 		return _GapName_2
 	default:
-		return fmt.Sprintf("Gap(%d)", i)
+		return ""
 	}
 }
 
diff --git a/testdata/num.go b/testdata/num.go
index 0d5ab10..f514ea5 100644
--- a/testdata/num.go
+++ b/testdata/num.go
@@ -19,13 +19,13 @@ const (
 )
 
 func main() {
-	ck(-3, "Num(-3)")
+	ck(-3, "")
 	ck(m_2, "m_2")
 	ck(m_1, "m_1")
 	ck(m0, "m0")
 	ck(m1, "m1")
 	ck(m2, "m2")
-	ck(3, "Num(3)")
+	ck(3, "")
 }
 
 func ck(num Num, str string) {
diff --git a/testdata/num.golden b/testdata/num.golden
index 97cc937..47d2ef4 100644
--- a/testdata/num.golden
+++ b/testdata/num.golden
@@ -5,12 +5,17 @@ var _NumIndex = [...]uint8{0, 3, 6, 8, 10, 12}
 
 const _NumLowerName = "m_2m_1m0m1m2"
 
-func (i Num) String() string {
+func (i Num) string() (string, error) {
 	i -= -2
 	if i < 0 || i >= Num(len(_NumIndex)-1) {
-		return fmt.Sprintf("Num(%d)", i+-2)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _NumName[_NumIndex[i]:_NumIndex[i+1]]
+	return _NumName[_NumIndex[i]:_NumIndex[i+1]], nil
+}
+
+func (i Num) String() string {
+	val, _ := i.string()
+	return val
 }
 
 func (Num) Values() []string {
diff --git a/testdata/number.go b/testdata/number.go
index 7f1c824..5b7b576 100644
--- a/testdata/number.go
+++ b/testdata/number.go
@@ -24,7 +24,7 @@ func main() {
 	ck(Two, "Two")
 	ck(Three, "Three")
 	ck(AnotherOne, "One")
-	ck(127, "Number(127)")
+	ck(127, "")
 }
 
 func ck(num Number, str string) {
diff --git a/testdata/offset.golden b/testdata/offset.golden
index 0e52817..d7983f2 100644
--- a/testdata/offset.golden
+++ b/testdata/offset.golden
@@ -5,12 +5,17 @@ var _NumberIndex = [...]uint8{0, 3, 6, 11}
 
 const _NumberLowerName = "onetwothree"
 
-func (i Number) String() string {
+func (i Number) string() (string, error) {
 	i -= 1
 	if i < 0 || i >= Number(len(_NumberIndex)-1) {
-		return fmt.Sprintf("Number(%d)", i+1)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _NumberName[_NumberIndex[i]:_NumberIndex[i+1]]
+	return _NumberName[_NumberIndex[i]:_NumberIndex[i+1]], nil
+}
+
+func (i Number) String() string {
+	val, _ := i.string()
+	return val
 }
 
 func (Number) Values() []string {
diff --git a/testdata/prime.go b/testdata/prime.go
index f551a1a..6502f0a 100644
--- a/testdata/prime.go
+++ b/testdata/prime.go
@@ -29,11 +29,11 @@ const (
 )
 
 func main() {
-	ck(0, "Prime(0)")
-	ck(1, "Prime(1)")
+	ck(0, "")
+	ck(1, "")
 	ck(p2, "p2")
 	ck(p3, "p3")
-	ck(4, "Prime(4)")
+	ck(4, "")
 	ck(p5, "p5")
 	ck(p7, "p7")
 	ck(p77, "p7")
@@ -46,7 +46,7 @@ func main() {
 	ck(p37, "p37")
 	ck(p41, "p41")
 	ck(p43, "p43")
-	ck(44, "Prime(44)")
+	ck(44, "")
 }
 
 func ck(prime Prime, str string) {
diff --git a/testdata/prime.golden b/testdata/prime.golden
index 8783338..3c54e43 100644
--- a/testdata/prime.golden
+++ b/testdata/prime.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 func (Prime) Values() []string {
diff --git a/testdata/primeGQLGen.golden b/testdata/primeGQLGen.golden
index 14c8eff..14822bc 100644
--- a/testdata/primeGQLGen.golden
+++ b/testdata/primeGQLGen.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/primeJson.golden b/testdata/primeJson.golden
index 9224728..beee577 100644
--- a/testdata/primeJson.golden
+++ b/testdata/primeJson.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/primeJsonAndSql.golden b/testdata/primeJsonAndSql.golden
index 1133b4a..27b5acb 100644
--- a/testdata/primeJsonAndSql.golden
+++ b/testdata/primeJsonAndSql.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
@@ -140,7 +145,7 @@ func (i *Prime) UnmarshalJSON(data []byte) error {
 }
 
 func (i Prime) Value() (driver.Value, error) {
-	return i.String(), nil
+	return i.string()
 }
 
 func (i *Prime) Scan(value interface{}) error {
diff --git a/testdata/primeSql.golden b/testdata/primeSql.golden
index 9a5292a..092fa70 100644
--- a/testdata/primeSql.golden
+++ b/testdata/primeSql.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
@@ -123,7 +128,7 @@ func (i Prime) IsAPrime() bool {
 }
 
 func (i Prime) Value() (driver.Value, error) {
-	return i.String(), nil
+	return i.string()
 }
 
 func (i *Prime) Scan(value interface{}) error {
diff --git a/testdata/primeText.golden b/testdata/primeText.golden
index e8102d6..1c4eb64 100644
--- a/testdata/primeText.golden
+++ b/testdata/primeText.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/primeYaml.golden b/testdata/primeYaml.golden
index 5197219..3b1b24e 100644
--- a/testdata/primeYaml.golden
+++ b/testdata/primeYaml.golden
@@ -18,11 +18,16 @@ var _PrimeMap = map[Prime]string{
 	43: _PrimeName[32:35],
 }
 
-func (i Prime) String() string {
+func (i Prime) string() (string, error) {
 	if str, ok := _PrimeMap[i]; ok {
-		return str
+		return str, nil
 	}
-	return fmt.Sprintf("Prime(%d)", i)
+	return "", fmt.Errorf("value is out of enum range")
+}
+
+func (i Prime) String() string {
+	str, _ := i.string()
+	return str
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
@@ -124,7 +129,7 @@ func (i Prime) IsAPrime() bool {
 
 // MarshalYAML implements a YAML Marshaler for Prime
 func (i Prime) MarshalYAML() (interface{}, error) {
-	return i.String(), nil
+	return i.string()
 }
 
 // UnmarshalYAML implements a YAML Unmarshaler for Prime
diff --git a/testdata/thresholdeq.go b/testdata/thresholdeq.go
index fd736b5..ef78042 100644
--- a/testdata/thresholdeq.go
+++ b/testdata/thresholdeq.go
@@ -18,25 +18,25 @@ const (
 )
 
 func main() {
-	ck(1, "Thresholdeq(1)")
+	ck(1, "")
 	ck(req1, "req1")
-	ck(3, "Thresholdeq(3)")
+	ck(3, "")
 	ck(req2, "req2")
-	ck(5, "Thresholdeq(5)")
+	ck(5, "")
 	ck(req3, "req3")
-	ck(7, "Thresholdeq(7)")
+	ck(7, "")
 	ck(req4, "req4")
-	ck(9, "Thresholdeq(9)")
+	ck(9, "")
 	ck(req5, "req5")
-	ck(11, "Thresholdeq(11)")
+	ck(11, "")
 	ck(req6, "req6")
-	ck(13, "Thresholdeq(13)")
+	ck(13, "")
 	ck(req7, "req7")
-	ck(15, "Thresholdeq(15)")
+	ck(15, "")
 	ck(req8, "req8")
-	ck(17, "Thresholdeq(17)")
+	ck(17, "")
 	ck(req9, "req9")
-	ck(19, "Thresholdeq(19)")
+	ck(19, "")
 	ck(req10, "req10")
 }
 
diff --git a/testdata/thresholdgt.go b/testdata/thresholdgt.go
index 88e589c..b76e906 100644
--- a/testdata/thresholdgt.go
+++ b/testdata/thresholdgt.go
@@ -19,27 +19,27 @@ const (
 )
 
 func main() {
-	ck(1, "Thresholdgt(1)")
+	ck(1, "")
 	ck(rgt1, "rgt1")
-	ck(3, "Thresholdgt(3)")
+	ck(3, "")
 	ck(rgt2, "rgt2")
-	ck(5, "Thresholdgt(5)")
+	ck(5, "")
 	ck(rgt3, "rgt3")
-	ck(7, "Thresholdgt(7)")
+	ck(7, "")
 	ck(rgt4, "rgt4")
-	ck(9, "Thresholdgt(9)")
+	ck(9, "")
 	ck(rgt5, "rgt5")
-	ck(11, "Thresholdgt(11)")
+	ck(11, "")
 	ck(rgt6, "rgt6")
-	ck(13, "Thresholdgt(13)")
+	ck(13, "")
 	ck(rgt7, "rgt7")
-	ck(15, "Thresholdgt(15)")
+	ck(15, "")
 	ck(rgt8, "rgt8")
-	ck(17, "Thresholdgt(17)")
+	ck(17, "")
 	ck(rgt9, "rgt9")
-	ck(19, "Thresholdgt(19)")
+	ck(19, "")
 	ck(rgt10, "rgt10")
-	ck(21, "Thresholdgt(21)")
+	ck(21, "")
 	ck(rgt11, "rgt11")
 }
 
@@ -47,4 +47,4 @@ func ck(thresholdgt Thresholdgt, str string) {
 	if fmt.Sprint(thresholdgt) != str {
 		panic("thresholdgt.go: " + str)
 	}
-}
\ No newline at end of file
+}
diff --git a/testdata/thresholdlt.go b/testdata/thresholdlt.go
index 603f382..cc1534c 100644
--- a/testdata/thresholdlt.go
+++ b/testdata/thresholdlt.go
@@ -17,23 +17,23 @@ const (
 )
 
 func main() {
-	ck(1, "Thresholdlt(1)")
+	ck(1, "")
 	ck(rlt1, "rlt1")
-	ck(3, "Thresholdlt(3)")
+	ck(3, "")
 	ck(rlt2, "rlt2")
-	ck(5, "Thresholdlt(5)")
+	ck(5, "")
 	ck(rlt3, "rlt3")
-	ck(7, "Thresholdlt(7)")
+	ck(7, "")
 	ck(rlt4, "rlt4")
-	ck(9, "Thresholdlt(9)")
+	ck(9, "")
 	ck(rlt5, "rlt5")
-	ck(11, "Thresholdlt(11)")
+	ck(11, "")
 	ck(rlt6, "rlt6")
-	ck(13, "Thresholdlt(13)")
+	ck(13, "")
 	ck(rlt7, "rlt7")
-	ck(15, "Thresholdlt(15)")
+	ck(15, "")
 	ck(rlt8, "rlt8")
-	ck(17, "Thresholdlt(17)")
+	ck(17, "")
 	ck(rlt9, "rlt9")
 }
 
diff --git a/testdata/transform_first.go b/testdata/transform_first.go
index f1f56c8..df52f77 100644
--- a/testdata/transform_first.go
+++ b/testdata/transform_first.go
@@ -14,8 +14,8 @@ func main() {
 	ck(Male, "M")
 	ck(Female, "F")
 	ck(unknown, "u")
-	ck(-127, "FirstCaseValue(-127)")
-	ck(127, "FirstCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value FirstCaseValue, str string) {
diff --git a/testdata/transform_first_lower.go b/testdata/transform_first_lower.go
index 865a265..0422624 100644
--- a/testdata/transform_first_lower.go
+++ b/testdata/transform_first_lower.go
@@ -14,8 +14,8 @@ func main() {
 	ck(Male, "m")
 	ck(Female, "f")
 	ck(Unknown, "u")
-	ck(-127, "FirstLowerCaseValue(-127)")
-	ck(127, "FirstLowerCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value FirstLowerCaseValue, str string) {
diff --git a/testdata/transform_first_upper.go b/testdata/transform_first_upper.go
index f7282a5..babf36d 100644
--- a/testdata/transform_first_upper.go
+++ b/testdata/transform_first_upper.go
@@ -14,8 +14,8 @@ func main() {
 	ck(male, "M")
 	ck(female, "F")
 	ck(unknown, "U")
-	ck(-127, "FirstUpperCaseValue(-127)")
-	ck(127, "FirstUpperCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value FirstUpperCaseValue, str string) {
diff --git a/testdata/transform_kebab.go b/testdata/transform_kebab.go
index 8af3704..17d9edc 100644
--- a/testdata/transform_kebab.go
+++ b/testdata/transform_kebab.go
@@ -14,8 +14,8 @@ func main() {
 	ck(KebabCaseValueOne, "kebab-case-value-one")
 	ck(KebabCaseValueTwo, "kebab-case-value-two")
 	ck(KebabCaseValueThree, "kebab-case-value-three")
-	ck(-127, "KebabCaseValue(-127)")
-	ck(127, "KebabCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value KebabCaseValue, str string) {
diff --git a/testdata/transform_kebab_upper.go b/testdata/transform_kebab_upper.go
index 1d15f9b..d9da854 100644
--- a/testdata/transform_kebab_upper.go
+++ b/testdata/transform_kebab_upper.go
@@ -14,8 +14,8 @@ func main() {
 	ck(KebabUpperCaseValueOne, "KEBAB-UPPER-CASE-VALUE-ONE")
 	ck(KebabUpperCaseValueTwo, "KEBAB-UPPER-CASE-VALUE-TWO")
 	ck(KebabUpperCaseValueThree, "KEBAB-UPPER-CASE-VALUE-THREE")
-	ck(-127, "KebabUpperCaseValue(-127)")
-	ck(127, "KebabUpperCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value KebabUpperCaseValue, str string) {
diff --git a/testdata/transform_lower.go b/testdata/transform_lower.go
index e9ebe29..88eff78 100644
--- a/testdata/transform_lower.go
+++ b/testdata/transform_lower.go
@@ -14,8 +14,8 @@ func main() {
 	ck(LowerCaseValueOne, "lowercasevalueone")
 	ck(LowerCaseValueTwo, "lowercasevaluetwo")
 	ck(LowerCaseValueThree, "lowercasevaluethree")
-	ck(-127, "LowerCaseValue(-127)")
-	ck(127, "LowerCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value LowerCaseValue, str string) {
diff --git a/testdata/transform_snake.go b/testdata/transform_snake.go
index c8cce88..ce44897 100644
--- a/testdata/transform_snake.go
+++ b/testdata/transform_snake.go
@@ -14,8 +14,8 @@ func main() {
 	ck(SnakeCaseValueOne, "snake_case_value_one")
 	ck(SnakeCaseValueTwo, "snake_case_value_two")
 	ck(SnakeCaseValueThree, "snake_case_value_three")
-	ck(-127, "SnakeCaseValue(-127)")
-	ck(127, "SnakeCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value SnakeCaseValue, str string) {
diff --git a/testdata/transform_snake_upper.go b/testdata/transform_snake_upper.go
index 46e41e1..ba40ff1 100644
--- a/testdata/transform_snake_upper.go
+++ b/testdata/transform_snake_upper.go
@@ -14,8 +14,8 @@ func main() {
 	ck(SnakeUpperCaseValueOne, "SNAKE_UPPER_CASE_VALUE_ONE")
 	ck(SnakeUpperCaseValueTwo, "SNAKE_UPPER_CASE_VALUE_TWO")
 	ck(SnakeUpperCaseValueThree, "SNAKE_UPPER_CASE_VALUE_THREE")
-	ck(-127, "SnakeUpperCaseValue(-127)")
-	ck(127, "SnakeUpperCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value SnakeUpperCaseValue, str string) {
diff --git a/testdata/transform_title.go b/testdata/transform_title.go
index a36a745..369d247 100644
--- a/testdata/transform_title.go
+++ b/testdata/transform_title.go
@@ -14,8 +14,8 @@ func main() {
 	ck(titlecasevalueone, "Titlecasevalueone")
 	ck(titlecasevaluetwo, "Titlecasevaluetwo")
 	ck(titlecasevaluethree, "Titlecasevaluethree")
-	ck(-127, "TitleCaseValue(-127)")
-	ck(127, "TitleCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value TitleCaseValue, str string) {
diff --git a/testdata/transform_upper.go b/testdata/transform_upper.go
index a18a4bf..e0efc67 100644
--- a/testdata/transform_upper.go
+++ b/testdata/transform_upper.go
@@ -14,8 +14,8 @@ func main() {
 	ck(UpperCaseValueOne, "UPPERCASEVALUEONE")
 	ck(UpperCaseValueTwo, "UPPERCASEVALUETWO")
 	ck(UpperCaseValueThree, "UPPERCASEVALUETHREE")
-	ck(-127, "UpperCaseValue(-127)")
-	ck(127, "UpperCaseValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value UpperCaseValue, str string) {
diff --git a/testdata/transform_whitespace.go b/testdata/transform_whitespace.go
index b3d552d..be155ca 100644
--- a/testdata/transform_whitespace.go
+++ b/testdata/transform_whitespace.go
@@ -14,8 +14,8 @@ func main() {
 	ck(WhitespaceSeparatedValueOne, "whitespace separated value one")
 	ck(WhitespaceSeparatedValueTwo, "whitespace separated value two")
 	ck(WhitespaceSeparatedValueThree, "whitespace separated value three")
-	ck(-127, "WhitespaceSeparatedValue(-127)")
-	ck(127, "WhitespaceSeparatedValue(127)")
+	ck(-127, "")
+	ck(127, "")
 }
 
 func ck(value WhitespaceSeparatedValue, str string) {
diff --git a/testdata/trimPrefix.golden b/testdata/trimPrefix.golden
index 52f063e..b919e75 100644
--- a/testdata/trimPrefix.golden
+++ b/testdata/trimPrefix.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 6, 13, 22, 30, 36, 44, 50}
 
 const _DayLowerName = "mondaytuesdaywednesdaythursdayfridaysaturdaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/trimPrefixMultiple.golden b/testdata/trimPrefixMultiple.golden
index 439ca92..1aa2d42 100644
--- a/testdata/trimPrefixMultiple.golden
+++ b/testdata/trimPrefixMultiple.golden
@@ -5,11 +5,16 @@ var _DayIndex = [...]uint8{0, 6, 13, 22, 30, 36, 44, 50}
 
 const _DayLowerName = "mondaytuesdaywednesdaythursdayfridaysaturdaysunday"
 
-func (i Day) String() string {
+func (i Day) string() (string, error) {
 	if i < 0 || i >= Day(len(_DayIndex)-1) {
-		return fmt.Sprintf("Day(%d)", i)
+		return "", fmt.Errorf("value is out of enum range")
 	}
-	return _DayName[_DayIndex[i]:_DayIndex[i+1]]
+	return _DayName[_DayIndex[i]:_DayIndex[i+1]], nil
+}
+
+func (i Day) String() string {
+	val, _ := i.string()
+	return val
 }
 
 // An "invalid array index" compiler error signifies that the constant values have changed.
diff --git a/testdata/unum.go b/testdata/unum.go
index 2f8508f..f1b3990 100644
--- a/testdata/unum.go
+++ b/testdata/unum.go
@@ -22,13 +22,13 @@ const (
 )
 
 func main() {
-	ck(^Unum(0)-3, "Unum(252)")
+	ck(^Unum(0)-3, "")
 	ck(m_2, "m_2")
 	ck(m_1, "m_1")
 	ck(m0, "m0")
 	ck(m1, "m1")
 	ck(m2, "m2")
-	ck(3, "Unum(3)")
+	ck(3, "")
 }
 
 func ck(unum Unum, str string) {
diff --git a/testdata/unum.golden b/testdata/unum.golden
index 9e413dc..d327701 100644
--- a/testdata/unum.golden
+++ b/testdata/unum.golden
@@ -19,7 +19,7 @@ func (i Unum) String() string {
 		i -= 253
 		return _UnumName_1[_UnumIndex_1[i]:_UnumIndex_1[i+1]]
 	default:
-		return fmt.Sprintf("Unum(%d)", i)
+		return ""
 	}
 }
 
diff --git a/testdata/unum2.go b/testdata/unum2.go
index edbbedf..a08fac5 100644
--- a/testdata/unum2.go
+++ b/testdata/unum2.go
@@ -20,8 +20,8 @@ func main() {
 	ck(Zero, "Zero")
 	ck(One, "One")
 	ck(Two, "Two")
-	ck(3, "Unum2(3)")
-	ck(255, "Unum2(255)")
+	ck(3, "")
+	ck(255, "")
 }
 
 func ck(unum Unum2, str string) {