diff --git a/mockgen/deprecated.go b/mockgen/deprecated.go
index 0b45a2e3..ec0451fa 100644
--- a/mockgen/deprecated.go
+++ b/mockgen/deprecated.go
@@ -7,8 +7,8 @@ import (
 )
 
 const (
-	deprecatedFlagProgOnly = "prog_only"
-	deprecatedFlagExecOnly = "exec_only"
+	_deprecatedFlagProgOnly = "prog_only"
+	_deprecatedFlagExecOnly = "exec_only"
 )
 
 var (
@@ -23,9 +23,9 @@ func notifyAboutDeprecatedFlags() {
 
 	flag.Visit(func(f *flag.Flag) {
 		switch f.Name {
-		case deprecatedFlagProgOnly:
+		case _deprecatedFlagProgOnly:
 			logger.Println("The -prog_only flag is deprecated and has no effect.", resetColorPostfix)
-		case deprecatedFlagExecOnly:
+		case _deprecatedFlagExecOnly:
 			logger.Println("The -exec_only flag is deprecated and has no effect.", resetColorPostfix)
 		}
 	})
diff --git a/mockgen/mockgen.go b/mockgen/mockgen.go
index 79cce84b..57bd3423 100644
--- a/mockgen/mockgen.go
+++ b/mockgen/mockgen.go
@@ -43,9 +43,7 @@ import (
 	"go.uber.org/mock/mockgen/model"
 )
 
-const (
-	gomockImportPath = "go.uber.org/mock/gomock"
-)
+const _gomockImportPath = "go.uber.org/mock/gomock"
 
 var (
 	version = ""
@@ -346,7 +344,7 @@ func (g *generator) Generate(pkg *model.Package, outputPkgName string, outputPac
 
 	// Get all required imports, and generate unique names for them all.
 	im := pkg.Imports()
-	im[gomockImportPath] = true
+	im[_gomockImportPath] = true
 
 	// Only import reflect if it's used. We only use reflect in mocked methods
 	// so only import if any of the mocked interfaces have methods.
diff --git a/mockgen/model/model.go b/mockgen/model/model.go
index 853dbf2d..16e7682a 100644
--- a/mockgen/model/model.go
+++ b/mockgen/model/model.go
@@ -23,8 +23,8 @@ import (
 	"strings"
 )
 
-// pkgPath is the importable path for package model
-const pkgPath = "go.uber.org/mock/mockgen/model"
+// _pkgPath is the importable path for package model
+const _pkgPath = "go.uber.org/mock/mockgen/model"
 
 // Package is a Go package. It may be a subset.
 type Package struct {
@@ -149,12 +149,12 @@ type Type interface {
 func init() {
 	// Call gob.RegisterName with pkgPath as prefix to avoid conflicting with
 	// github.com/golang/mock/mockgen/model 's registration.
-	gob.RegisterName(pkgPath+".ArrayType", &ArrayType{})
-	gob.RegisterName(pkgPath+".ChanType", &ChanType{})
-	gob.RegisterName(pkgPath+".FuncType", &FuncType{})
-	gob.RegisterName(pkgPath+".MapType", &MapType{})
-	gob.RegisterName(pkgPath+".NamedType", &NamedType{})
-	gob.RegisterName(pkgPath+".PointerType", &PointerType{})
+	gob.RegisterName(_pkgPath+".ArrayType", &ArrayType{})
+	gob.RegisterName(_pkgPath+".ChanType", &ChanType{})
+	gob.RegisterName(_pkgPath+".FuncType", &FuncType{})
+	gob.RegisterName(_pkgPath+".MapType", &MapType{})
+	gob.RegisterName(_pkgPath+".NamedType", &NamedType{})
+	gob.RegisterName(_pkgPath+".PointerType", &PointerType{})
 
 	// Call gob.RegisterName to make sure it has the consistent name registered
 	// for both gob decoder and encoder.
@@ -163,7 +163,7 @@ func init() {
 	// calling rt.PkgPath() for a name to register. If your project has vendor
 	// directory, it is possible that PkgPath will get a path like this:
 	//     ../../../vendor/go.uber.org/mock/mockgen/model
-	gob.RegisterName(pkgPath+".PredeclaredType", PredeclaredType(""))
+	gob.RegisterName(_pkgPath+".PredeclaredType", PredeclaredType(""))
 }
 
 // ArrayType is an array or slice type.