diff --git a/ogenregex/ogenregex.go b/ogenregex/ogenregex.go
index 4cc0f7e56..5fc22c143 100644
--- a/ogenregex/ogenregex.go
+++ b/ogenregex/ogenregex.go
@@ -22,7 +22,8 @@ var _ = []Regexp{
 }
 
 type goRegexp struct {
-	exp *regexp.Regexp
+	orig string
+	exp  *regexp.Regexp
 }
 
 func (r goRegexp) Match(s []byte) (bool, error) {
@@ -34,7 +35,7 @@ func (r goRegexp) MatchString(s string) (bool, error) {
 }
 
 func (r goRegexp) String() string {
-	return r.exp.String()
+	return r.orig
 }
 
 type regexp2Regexp struct {
@@ -67,7 +68,7 @@ type Regexp interface {
 func Compile(exp string) (Regexp, error) {
 	if converted, ok := Convert(exp); ok {
 		if re, err := regexp.Compile(converted); err == nil {
-			return goRegexp{re}, nil
+			return goRegexp{orig: exp, exp: re}, nil
 		}
 	}
 	re, err := regexp2.Compile(exp, regexp2.ECMAScript|regexp2.Unicode)
diff --git a/ogenregex/ogenregex_test.go b/ogenregex/ogenregex_test.go
index bb6d09b47..39a9c3fcd 100644
--- a/ogenregex/ogenregex_test.go
+++ b/ogenregex/ogenregex_test.go
@@ -9,68 +9,68 @@ import (
 
 func TestCompile(t *testing.T) {
 	type testCase struct {
-		input      string
-		wantType   Regexp
-		wantString string
-		wantErr    bool
+		input    string
+		wantType Regexp
+		wantErr  bool
 	}
 
 	tests := []testCase{
 		// Conversion is not required.
-		{`\x20`, goRegexp{}, `\x20`, false},
-		{`\v`, goRegexp{}, `\v`, false},
-		{`\t`, goRegexp{}, `\t`, false},
-		{`\n`, goRegexp{}, `\n`, false},
-		{`\d`, goRegexp{}, `\d`, false},
-		{`\w`, goRegexp{}, `\w`, false},
-		{`\w{1}`, goRegexp{}, `\w{1}`, false},
-		{`\w{1,}`, goRegexp{}, `\w{1,}`, false},
-		{`\w{1,2}`, goRegexp{}, `\w{1,2}`, false},
-		{`\b`, goRegexp{}, `\b`, false},
-		{`\B`, goRegexp{}, `\B`, false},
-		{`\.`, goRegexp{}, `\.`, false},
-		{`\[`, goRegexp{}, `\[`, false},
-		{`\]`, goRegexp{}, `\]`, false},
-		{`\(`, goRegexp{}, `\(`, false},
-		{`\)`, goRegexp{}, `\)`, false},
-		{`\{`, goRegexp{}, `\{`, false},
-		{`\}`, goRegexp{}, `\}`, false},
-		{`\\`, goRegexp{}, `\\`, false},
-		{`\$`, goRegexp{}, `\$`, false},
+		{`\0`, goRegexp{}, false},
+		{`\x20`, goRegexp{}, false},
+		{`\v`, goRegexp{}, false},
+		{`\t`, goRegexp{}, false},
+		{`\n`, goRegexp{}, false},
+		{`\d`, goRegexp{}, false},
+		{`\w`, goRegexp{}, false},
+		{`\w{1}`, goRegexp{}, false},
+		{`\w{1,}`, goRegexp{}, false},
+		{`\w{1,2}`, goRegexp{}, false},
+		{`\b`, goRegexp{}, false},
+		{`\B`, goRegexp{}, false},
+		{`\.`, goRegexp{}, false},
+		{`\[`, goRegexp{}, false},
+		{`\]`, goRegexp{}, false},
+		{`\(`, goRegexp{}, false},
+		{`\)`, goRegexp{}, false},
+		{`\{`, goRegexp{}, false},
+		{`\}`, goRegexp{}, false},
+		{`\\`, goRegexp{}, false},
+		{`\$`, goRegexp{}, false},
 
 		// Simplification.
-		{`\u000a`, goRegexp{}, `\x{000a}`, false},
-		{`\u{000a}`, goRegexp{}, `\x{000a}`, false},
+		{`\u000a`, goRegexp{}, false},
+		{`\u{000a}`, goRegexp{}, false},
 		// "\z" just unnecessarily escapes the 'z'.
-		{`\z`, goRegexp{}, `z`, false},
+		{`\z`, goRegexp{}, false},
 
 		// Conversion is required.
 		//
 		// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Character_Classes#types.
 		//
 		// In ECMA-262, \c + [a-fA-F] is a control character.
-		{`\ca`, goRegexp{}, `\x01`, false},
-		{`\cA`, goRegexp{}, `\x01`, false},
-		{`\cb`, goRegexp{}, `\x02`, false},
-		{`\cB`, goRegexp{}, `\x02`, false},
+		{`\ca`, goRegexp{}, false},
+		{`\cA`, goRegexp{}, false},
+		{`\cb`, goRegexp{}, false},
+		{`\cB`, goRegexp{}, false},
 		// In ECMA-262, \b in a character class is a backspace.
-		{`[\b]`, goRegexp{}, `[\x08]`, false},
+		{`[\b]`, goRegexp{}, false},
 		// ECMA-262 dot matches any single character except line terminators: \n, \r, \u2028 or \u2029.
-		{`.*`, goRegexp{}, re2Dot + `*`, false},
+		{`.*`, goRegexp{}, false},
 		// Whitespace characters in ECMA-262 differ from those in RE2.
 		//
 		// Whitespace characters in ECMA-262:
 		// [ \f\n\r\t\v\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]
-		{`\s`, goRegexp{}, `[` + whitespaceChars + `]`, false},
-		{`\S`, goRegexp{}, `[^` + whitespaceChars + `]`, false},
-		{`[\s]`, goRegexp{}, `[` + whitespaceChars + `]`, false},
+		{`\s`, goRegexp{}, false},
+		{`\S`, goRegexp{}, false},
+		{`[\s]`, goRegexp{}, false},
 
 		// Use regexp2.
-		{`^(?!examples/)`, regexp2Regexp{}, `^(?!examples/)`, false},
+		{`^(?!examples/)`, regexp2Regexp{}, false},
 
 		// Error.
-		{")", nil, ``, true},
-		{"(?`)", nil, ``, true},
+		{")", nil, true},
+		{"(?`)", nil, true},
 	}
 	for i, tt := range tests {
 		tt := tt
@@ -87,7 +87,84 @@ func TestCompile(t *testing.T) {
 			a.NoError(err)
 			a.NotPanics(func() { MustCompile(tt.input) })
 			a.IsType(tt.wantType, got)
-			a.Equal(tt.wantString, got.String())
+			a.Equal(tt.input, got.String())
+		})
+	}
+}
+
+func TestConvert(t *testing.T) {
+	type testCase struct {
+		input      string
+		wantString string
+		wantOk     bool
+	}
+
+	tests := []testCase{
+		// Conversion is not required.
+		{`\0`, `\0`, true},
+		{`\x20`, `\x20`, true},
+		{`\v`, `\v`, true},
+		{`\t`, `\t`, true},
+		{`\n`, `\n`, true},
+		{`\d`, `\d`, true},
+		{`\w`, `\w`, true},
+		{`\w{1}`, `\w{1}`, true},
+		{`\w{1,}`, `\w{1,}`, true},
+		{`\w{1,2}`, `\w{1,2}`, true},
+		{`\b`, `\b`, true},
+		{`\B`, `\B`, true},
+		{`\.`, `\.`, true},
+		{`\[`, `\[`, true},
+		{`\]`, `\]`, true},
+		{`\(`, `\(`, true},
+		{`\)`, `\)`, true},
+		{`\{`, `\{`, true},
+		{`\}`, `\}`, true},
+		{`\\`, `\\`, true},
+		{`\$`, `\$`, true},
+
+		// Simplification.
+		{`\u000a`, `\x{000a}`, true},
+		{`\u{000a}`, `\x{000a}`, true},
+		// "\z" just unnecessarily escapes the 'z'.
+		{`\z`, `z`, true},
+
+		// Conversion is required.
+		//
+		// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Character_Classes#types.
+		//
+		// In ECMA-262, \c + [a-fA-F] is a control character.
+		{`\ca`, `\x01`, true},
+		{`\cA`, `\x01`, true},
+		{`\cb`, `\x02`, true},
+		{`\cB`, `\x02`, true},
+		// In ECMA-262, \b in a character class is a backspace.
+		{`[\b]`, `[\x08]`, true},
+		// ECMA-262 dot matches any single character except line terminators: \n, \r, \u2028 or \u2029.
+		{`.*`, re2Dot + `*`, true},
+		// Whitespace characters in ECMA-262 differ from those in RE2.
+		//
+		// Whitespace characters in ECMA-262:
+		// [ \f\n\r\t\v\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]
+		{`\s`, `[` + whitespaceChars + `]`, true},
+		{`\S`, `[^` + whitespaceChars + `]`, true},
+		{`[\s]`, `[` + whitespaceChars + `]`, true},
+
+		// Use regexp2.
+		{`^(?!examples/)`, ``, false},
+
+		// Error.
+		{")", ``, false},
+		{"(?`)", ``, false},
+	}
+	for i, tt := range tests {
+		tt := tt
+		t.Run(fmt.Sprintf("Test%d", i+1), func(t *testing.T) {
+			a := require.New(t)
+
+			got, ok := Convert(tt.input)
+			a.Equal(tt.wantOk, ok, "%q", tt.input)
+			a.Equal(tt.wantString, got)
 		})
 	}
 }