diff --git a/CHANGELOG.md b/CHANGELOG.md
index 88d7540..80b1700 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,13 +9,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- The index now supports whitespace and punctuation folding ([#25](https://github.com/ianlewis/go-stardict/issues/25))
-- The synonym index (.syn) file is now supported ([#2](https://github.com/ianlewis/go-stardict/issues/2))
-- `Stardict.Search` and `Idx.Search` now support queries in glob format ([#21](https://github.com/ianlewis/go-stardict/issues/21))
+- The index now supports whitespace and punctuation folding ([#25](https://github.com/ianlewis/go-stardict/issues/25)).
+- The synonym index (.syn) file is now supported ([#2](https://github.com/ianlewis/go-stardict/issues/2)).
+- `Stardict.Search` and `Idx.Search` now support queries in glob format ([#21](https://github.com/ianlewis/go-stardict/issues/21)).
 
 ### Changed
 
 - The minimum supported Go version is now 1.23.
+- `stardict.Open` and `stardict.OpenAll` now take an `options` argument which allows for specifying options for opening dictionaries ([#87](https://github.com/ianlewis/go-stardict/issues/87)).
+- `stardict.idx.Options.Folder` is now a constructor `func() transform.Transformer` rather than a static `golang.org/x/text/transform.Transformer` value ([#87](https://github.com/ianlewis/go-stardict/issues/87)).
 
 ## [0.1.0] - 2024-11-04
 
diff --git a/idx/idx.go b/idx/idx.go
index 3e07adc..845e45f 100644
--- a/idx/idx.go
+++ b/idx/idx.go
@@ -63,8 +63,9 @@ func (w *foldedWord) String() string {
 
 // Options are options for the idx data.
 type Options struct {
-	// Folder is the transformer that performs folding on index entries.
-	Folder transform.Transformer
+	// Folder returns a [transform.Transformer] that performs folding (e.g.
+	// case folding, whitespace folding, etc.) on index entries.
+	Folder func() transform.Transformer
 
 	// ScannerOptions are the options to use when reading the .idx file.
 	ScannerOptions *ScannerOptions
@@ -72,7 +73,9 @@ type Options struct {
 
 // DefaultOptions is the default options for an Idx.
 var DefaultOptions = &Options{
-	Folder: transform.Nop,
+	Folder: func() transform.Transformer {
+		return transform.Nop
+	},
 	ScannerOptions: &ScannerOptions{
 		OffsetBits: 32,
 	},
@@ -87,7 +90,7 @@ type Idx struct {
 	index *index.Index[*foldedWord]
 
 	// foldTransformer performs folding on text.
-	foldTransformer transform.Transformer
+	foldTransformer func() transform.Transformer
 }
 
 // New returns a new in-memory index.
@@ -117,7 +120,7 @@ func NewWithSyn(idxReader, synReader io.ReadCloser, options *Options) (*Idx, err
 	var words []*foldedWord
 	for s.Scan() {
 		word := s.Word()
-		folded, _, err := transform.String(idx.foldTransformer, word.Word)
+		folded, _, err := transform.String(idx.foldTransformer(), word.Word)
 		if err != nil {
 			return nil, fmt.Errorf("folding word %q: %w", word.Word, err)
 		}
@@ -139,7 +142,7 @@ func NewWithSyn(idxReader, synReader io.ReadCloser, options *Options) (*Idx, err
 		}
 		for synScanner.Scan() {
 			word := synScanner.Word()
-			folded, _, err := transform.String(idx.foldTransformer, word.Word)
+			folded, _, err := transform.String(idx.foldTransformer(), word.Word)
 			if err != nil {
 				return nil, fmt.Errorf("folding word %q: %w", word.Word, err)
 			}
@@ -304,7 +307,7 @@ func (idx *Idx) foldGlob(q string) (string, error) {
 		if syntax.Special(c) {
 			if !isSpecial {
 				if b.Len() > 0 {
-					w, _, err := transform.String(idx.foldTransformer, b.String())
+					w, _, err := transform.String(idx.foldTransformer(), b.String())
 					if err != nil {
 						return "", fmt.Errorf("folding query %q: %w", q, err)
 					}
@@ -330,7 +333,7 @@ func (idx *Idx) foldGlob(q string) (string, error) {
 	w := b.String()
 	if !isSpecial {
 		// fold the word
-		fw, _, err := transform.String(idx.foldTransformer, w)
+		fw, _, err := transform.String(idx.foldTransformer(), w)
 		if err != nil {
 			return "", fmt.Errorf("folding query %q: %w", q, err)
 		}
diff --git a/idx/idx_test.go b/idx/idx_test.go
index ce84ae0..9694f26 100644
--- a/idx/idx_test.go
+++ b/idx/idx_test.go
@@ -22,6 +22,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-cmp/cmp/cmpopts"
 	"golang.org/x/text/cases"
+	"golang.org/x/text/transform"
 
 	"github.com/ianlewis/go-stardict/idx"
 	"github.com/ianlewis/go-stardict/internal/testutil"
@@ -222,7 +223,9 @@ func TestIdx_Search(t *testing.T) {
 			},
 			idxoffsetbits: 32,
 			options: &idx.Options{
-				Folder: cases.Fold(),
+				Folder: func() transform.Transformer {
+					return cases.Fold()
+				},
 			},
 
 			expected: []*idx.Word{
@@ -261,7 +264,9 @@ func TestIdx_Search(t *testing.T) {
 			},
 			idxoffsetbits: 32,
 			options: &idx.Options{
-				Folder: cases.Fold(),
+				Folder: func() transform.Transformer {
+					return cases.Fold()
+				},
 			},
 
 			// NOTE: The returned index word is the value in the index
@@ -300,7 +305,9 @@ func TestIdx_Search(t *testing.T) {
 			},
 			idxoffsetbits: 32,
 			options: &idx.Options{
-				Folder: cases.Fold(),
+				Folder: func() transform.Transformer {
+					return cases.Fold()
+				},
 			},
 
 			expected: nil,
@@ -331,7 +338,9 @@ func TestIdx_Search(t *testing.T) {
 			},
 			idxoffsetbits: 32,
 			options: &idx.Options{
-				Folder: cases.Fold(),
+				Folder: func() transform.Transformer {
+					return cases.Fold()
+				},
 			},
 
 			expected: nil,
diff --git a/stardict.go b/stardict.go
index 4856d42..9af1509 100644
--- a/stardict.go
+++ b/stardict.go
@@ -62,13 +62,14 @@ type Stardict struct {
 	description      string
 	sametypesequence []dict.DataType
 
-	folder transform.Transformer
+	folder func() transform.Transformer
 }
 
 // Options are options for the Stardict dictionary.
 type Options struct {
-	// Folder performs folding (e.g. case folding, whitespace folding, etc.) on dictionary entries.
-	Folder transform.Transformer
+	// Folder returns a [transform.Transformer] that performs folding (e.g.
+	// case folding, whitespace folding, etc.) on dictionary entries.
+	Folder func() transform.Transformer
 }
 
 var (
@@ -109,23 +110,25 @@ func OpenAll(path string, options *Options) ([]*Stardict, []error) {
 func Open(path string, options *Options) (*Stardict, error) {
 	if options == nil {
 		options = &Options{
-			Folder: transform.Chain(
-				// Unicode Normalization Form D (Canonical Decomposition.
-				norm.NFD,
-				// Perform case folding.
-				cases.Fold(),
-				// Perform whitespace folding.
-				&folding.WhitespaceFolder{},
-				// Remove Non-spacing marks ([, ] {, }, etc.).
-				runes.Remove(runes.In(unicode.Mn)),
-				// Remove punctuation.
-				runes.Remove(runes.In(unicode.P)),
-				// Unicode Normalization Form C (Canonical Decomposition, followed by Canonical Composition)
-				// NOTE: Case folding does not normalize the input and may not
-				// preserve a normal form. Canonical Decomposition is thus necessary
-				// to be performed a second time.
-				norm.NFC,
-			),
+			Folder: func() transform.Transformer {
+				return transform.Chain(
+					// Unicode Normalization Form D (Canonical Decomposition.
+					norm.NFD,
+					// Perform case folding.
+					cases.Fold(),
+					// Perform whitespace folding.
+					&folding.WhitespaceFolder{},
+					// Remove Non-spacing marks ([, ] {, }, etc.).
+					runes.Remove(runes.In(unicode.Mn)),
+					// Remove punctuation.
+					runes.Remove(runes.In(unicode.P)),
+					// Unicode Normalization Form C (Canonical Decomposition, followed by Canonical Composition)
+					// NOTE: Case folding does not normalize the input and may not
+					// preserve a normal form. Canonical Decomposition is thus necessary
+					// to be performed a second time.
+					norm.NFC,
+				)
+			},
 		}
 	}
 
@@ -134,7 +137,9 @@ func Open(path string, options *Options) (*Stardict, error) {
 		idxoffsetbits: 32,
 	}
 
-	s.folder = transform.Nop
+	s.folder = func() transform.Transformer {
+		return transform.Nop
+	}
 	if options.Folder != nil {
 		s.folder = options.Folder
 	}
diff --git a/syn/syn.go b/syn/syn.go
index ec20a23..91adf0a 100644
--- a/syn/syn.go
+++ b/syn/syn.go
@@ -48,13 +48,16 @@ func (w *foldedWord) String() string {
 
 // Options are options for the idx data.
 type Options struct {
-	// Folder is the transformer that performs folding on index entries.
-	Folder transform.Transformer
+	// Folder returns a [transform.Transformer] that performs folding (e.g.
+	// case folding, whitespace folding, etc.) on index entries.
+	Folder func() transform.Transformer
 }
 
 // DefaultOptions is the default options for a Syn.
 var DefaultOptions = &Options{
-	Folder: transform.Nop,
+	Folder: func() transform.Transformer {
+		return transform.Nop
+	},
 }
 
 // Syn is is the synonym index. It is largely a map of synonym words to related
@@ -64,7 +67,7 @@ type Syn struct {
 	index *index.Index[*foldedWord]
 
 	// foldTransformer performs folding on text.
-	foldTransformer transform.Transformer
+	foldTransformer func() transform.Transformer
 }
 
 // New returns a new Syn by reading the data from r.
@@ -89,7 +92,7 @@ func New(r io.ReadCloser, options *Options) (*Syn, error) {
 	var words []*foldedWord
 	for s.Scan() {
 		word := s.Word()
-		folded, _, err := transform.String(syn.foldTransformer, word.Word)
+		folded, _, err := transform.String(syn.foldTransformer(), word.Word)
 		if err != nil {
 			return nil, fmt.Errorf("folding word %q: %w", word.Word, err)
 		}
@@ -168,7 +171,7 @@ func Open(ifoPath string) (*os.File, error) {
 
 // Search performs a query of the index and returns matching words.
 func (syn *Syn) Search(query string) ([]*Word, error) {
-	foldedQuery, _, err := transform.String(syn.foldTransformer, query)
+	foldedQuery, _, err := transform.String(syn.foldTransformer(), query)
 	if err != nil {
 		return nil, fmt.Errorf("folding query %q: %w", query, err)
 	}