diff --git a/file.go b/file.go
index d50a65b..aacf15e 100644
--- a/file.go
+++ b/file.go
@@ -4,6 +4,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"unicode"
 )
 
 // SelectFile displays the file selection dialog.
@@ -69,6 +70,8 @@ func Filename(filename string) Option {
 
 // FileFilter is an Option that sets a filename filter.
 //
+// On Windows and macOS filtering is always case-insensitive.
+//
 // macOS hides filename filters from the user,
 // and only supports filtering by extension
 // (or "uniform type identifiers").
@@ -78,6 +81,7 @@ func Filename(filename string) Option {
 type FileFilter struct {
 	Name     string   // display string that describes the filter (optional)
 	Patterns []string // filter patterns for the display string
+	CaseFold bool     // if set patterns are matched case-insensitively
 }
 
 func (f FileFilter) apply(o *options) {
@@ -91,7 +95,7 @@ func (f FileFilters) apply(o *options) {
 	o.fileFilters = append(o.fileFilters, f...)
 }
 
-// Windows' patterns need a name.
+// Windows patterns need a name.
 func (f FileFilters) name() {
 	for i, filter := range f {
 		if filter.Name == "" {
@@ -100,47 +104,42 @@ func (f FileFilters) name() {
 	}
 }
 
-// Windows' patterns are case insensitive, don't support character classes or escaping.
+// Windows patterns are case-insensitive, don't support character classes or escaping.
 //
 // First we remove character classes, then escaping. Patterns with literal wildcards are invalid.
 // The semicolon is a separator, so we replace it with the single character wildcard.
-// Empty and invalid filters/patterns are ignored.
 func (f FileFilters) simplify() {
-	var i = 0
-	for _, filter := range f {
+	for i := range f {
 		var j = 0
-		for _, pattern := range filter.Patterns {
+		for _, pattern := range f[i].Patterns {
 			var escape, invalid bool
 			var buf strings.Builder
-			for _, r := range removeClasses(pattern) {
-				if !escape && r == '\\' {
+			for _, b := range []byte(removeClasses(pattern)) {
+				if !escape && b == '\\' {
 					escape = true
 					continue
 				}
-				if escape && (r == '*' || r == '?') {
+				if escape && (b == '*' || b == '?') {
 					invalid = true
 					break
 				}
-				if r == ';' {
-					r = '?'
+				if b == ';' {
+					b = '?'
 				}
-				buf.WriteRune(r)
+				buf.WriteByte(b)
 				escape = false
 			}
 			if buf.Len() > 0 && !invalid {
-				filter.Patterns[j] = buf.String()
+				f[i].Patterns[j] = buf.String()
 				j++
 			}
 		}
-		if j > 0 {
-			filter.Patterns = filter.Patterns[:j]
-			f[i] = filter
-			i++
+		if j != 0 {
+			f[i].Patterns = f[i].Patterns[:j]
+		} else {
+			f[i].Patterns = nil
 		}
 	}
-	for ; i < len(f); i++ {
-		f[i] = FileFilter{}
-	}
 }
 
 // macOS types may be specified as extension strings without the leading period,
@@ -163,17 +162,17 @@ func (f FileFilters) types() []string {
 
 			var escape bool
 			var buf strings.Builder
-			for _, r := range removeClasses(ext) {
+			for _, b := range []byte(removeClasses(ext)) {
 				switch {
 				case escape:
 					escape = false
-				case r == '\\':
+				case b == '\\':
 					escape = true
 					continue
-				case r == '*' || r == '?':
+				case b == '*' || b == '?':
 					return nil
 				}
-				buf.WriteRune(r)
+				buf.WriteByte(b)
 			}
 			if buf.Len() > 0 {
 				res = append(res, buf.String())
@@ -187,8 +186,57 @@ func (f FileFilters) types() []string {
 	return append([]string{""}, res...)
 }
 
+// Unix patterns are case-sensitive. Fold them if requested.
+func (f FileFilters) casefold() {
+	for i := range f {
+		if !f[i].CaseFold {
+			continue
+		}
+		for j, pattern := range f[i].Patterns {
+			var class = -1
+			var escape bool
+			var buf strings.Builder
+			for i, r := range pattern {
+				switch {
+				case escape:
+					escape = false
+				case r == '\\':
+					escape = true
+				case class < 0:
+					if r == '[' {
+						class = i
+					}
+				case class < i-1:
+					if r == ']' {
+						class = -1
+					}
+				}
+
+				nr := unicode.SimpleFold(r)
+				if r == nr {
+					buf.WriteRune(r)
+					continue
+				}
+
+				if class < 0 {
+					buf.WriteByte('[')
+				}
+				buf.WriteRune(r)
+				for r != nr {
+					buf.WriteRune(nr)
+					nr = unicode.SimpleFold(nr)
+				}
+				if class < 0 {
+					buf.WriteByte(']')
+				}
+			}
+			f[i].Patterns[j] = buf.String()
+		}
+	}
+}
+
 // Remove character classes from pattern, assuming case insensitivity.
-// Classes of one character (case insensitive) are replaced by the character.
+// Classes of one character (case-insensitive) are replaced by the character.
 // Others are replaced by the single character wildcard.
 func removeClasses(pattern string) string {
 	var res strings.Builder
@@ -229,7 +277,7 @@ func removeClasses(pattern string) string {
 // Find a character class in the pattern.
 func findClass(pattern string) (start, end int) {
 	start = -1
-	escape := false
+	var escape bool
 	for i, b := range []byte(pattern) {
 		switch {
 		case escape:
@@ -240,7 +288,7 @@ func findClass(pattern string) (start, end int) {
 			if b == '[' {
 				start = i
 			}
-		case 0 <= start && start < i-1:
+		case start < i-1:
 			if b == ']' {
 				return start, i + 1
 			}
diff --git a/file_filter_test.go b/file_filter_test.go
index e95b7fd..22ae48c 100644
--- a/file_filter_test.go
+++ b/file_filter_test.go
@@ -10,9 +10,9 @@ func TestFileFilters_name(t *testing.T) {
 		data FileFilters
 		want string
 	}{
-		{FileFilters{{"", []string{`*.png`}}}, "*.png"},
-		{FileFilters{{"", []string{`*.png`, `*.jpg`}}}, "*.png *.jpg"},
-		{FileFilters{{"Image files", []string{`*.png`, `*.jpg`}}}, "Image files"},
+		{FileFilters{{"", []string{`*.png`}, true}}, "*.png"},
+		{FileFilters{{"", []string{`*.png`, `*.jpg`}, true}}, "*.png *.jpg"},
+		{FileFilters{{"Image files", []string{`*.png`, `*.jpg`}, true}}, "Image files"},
 	}
 	for i, tt := range tests {
 		tt.data.name()
@@ -24,57 +24,88 @@ func TestFileFilters_name(t *testing.T) {
 
 func TestFileFilters_simplify(t *testing.T) {
 	tests := []struct {
-		data FileFilters
+		data []string
 		want []string
 	}{
-		{FileFilters{{"", []string{``}}}, nil},
-		{FileFilters{{"", []string{`*.png`}}}, []string{"*.png"}},
-		{FileFilters{{"", []string{`*.pn?`}}}, []string{"*.pn?"}},
-		{FileFilters{{"", []string{`*.pn;`}}}, []string{"*.pn?"}},
-		{FileFilters{{"", []string{`*.pn\?`}}}, nil},
-		{FileFilters{{"", []string{`*.[PpNnGg]`}}}, []string{"*.?"}},
-		{FileFilters{{"", []string{`*.[Pp][Nn][Gg]`}}}, []string{"*.PNG"}},
-		{FileFilters{{"", []string{`*.[Pp][\Nn][G\g]`}}}, []string{"*.PNG"}},
-		{FileFilters{{"", []string{`*.[PNG`}}}, []string{"*.[PNG"}},
-		{FileFilters{{"", []string{`*.]PNG`}}}, []string{"*.]PNG"}},
-		{FileFilters{{"", []string{`*.[[]PNG`}}}, []string{"*.[PNG"}},
-		{FileFilters{{"", []string{`*.[]]PNG`}}}, []string{"*.]PNG"}},
-		{FileFilters{{"", []string{`*.[\[]PNG`}}}, []string{"*.[PNG"}},
-		{FileFilters{{"", []string{`*.[\]]PNG`}}}, []string{"*.]PNG"}},
-		{FileFilters{{"", []string{`public.png`}}}, []string{"public.png"}},
+		{[]string{``}, nil},
+		{[]string{`*.\?`}, nil},
+		{[]string{`*.png`}, []string{"*.png"}},
+		{[]string{`*.pn?`}, []string{"*.pn?"}},
+		{[]string{`*.pn;`}, []string{"*.pn?"}},
+		{[]string{`*.[PpNnGg]`}, []string{"*.?"}},
+		{[]string{`*.[Pp][Nn][Gg]`}, []string{"*.PNG"}},
+		{[]string{`*.[Pp][\Nn][G\g]`}, []string{"*.PNG"}},
+		{[]string{`*.[PNG`}, []string{"*.[PNG"}},
+		{[]string{`*.]PNG`}, []string{"*.]PNG"}},
+		{[]string{`*.[[]PNG`}, []string{"*.[PNG"}},
+		{[]string{`*.[]]PNG`}, []string{"*.]PNG"}},
+		{[]string{`*.[\[]PNG`}, []string{"*.[PNG"}},
+		{[]string{`*.[\]]PNG`}, []string{"*.]PNG"}},
+		{[]string{`public.png`}, []string{"public.png"}},
 	}
 	for i, tt := range tests {
-		tt.data.simplify()
-		if got := tt.data[0].Patterns; !reflect.DeepEqual(got, tt.want) {
+		filters := FileFilters{FileFilter{Patterns: tt.data}}
+		filters.simplify()
+		if got := filters[0].Patterns; !reflect.DeepEqual(got, tt.want) {
 			t.Errorf("FileFilters.simplify[%d] = %q; want %q", i, got, tt.want)
 		}
 	}
 }
 
+func TestFileFilters_casefold(t *testing.T) {
+	tests := []struct {
+		data []string
+		want []string
+	}{
+		{[]string{`*.png`}, []string{`*.[pP][nN][gG]`}},
+		{[]string{`*.pn?`}, []string{`*.[pP][nN]?`}},
+		{[]string{`*.pn;`}, []string{`*.[pP][nN];`}},
+		{[]string{`*.pn\?`}, []string{`*.[pP][nN]\?`}},
+		{[]string{`*.[PpNnGg]`}, []string{`*.[PppPNnnNGggG]`}},
+		{[]string{`*.[Pp][Nn][Gg]`}, []string{`*.[PppP][NnnN][GggG]`}},
+		{[]string{`*.[Pp][\Nn][G\g]`}, []string{`*.[PppP][\NnnN][Gg\gG]`}},
+		{[]string{`*.[PNG`}, []string{`*.[PpNnGg`}},
+		{[]string{`*.]PNG`}, []string{`*.][Pp][Nn][Gg]`}},
+		{[]string{`*.[[]PNG`}, []string{`*.[[][Pp][Nn][Gg]`}},
+		{[]string{`*.[]]PNG`}, []string{`*.[]][Pp][Nn][Gg]`}},
+		{[]string{`*.[\[]PNG`}, []string{`*.[\[][Pp][Nn][Gg]`}},
+		{[]string{`*.[\]]PNG`}, []string{`*.[\]][Pp][Nn][Gg]`}},
+	}
+	for i, tt := range tests {
+		filters := FileFilters{FileFilter{Patterns: tt.data}}
+		filters[0].CaseFold = true
+		filters.casefold()
+		if got := filters[0].Patterns; !reflect.DeepEqual(got, tt.want) {
+			t.Errorf("FileFilters.casefold[%d] = %q; want %q", i, got, tt.want)
+		}
+	}
+}
+
 func TestFileFilters_types(t *testing.T) {
 	tests := []struct {
-		data FileFilters
+		data []string
 		want []string
 	}{
-		{FileFilters{{"", []string{``}}}, nil},
-		{FileFilters{{"", []string{`*.png`}}}, []string{"", "png"}},
-		{FileFilters{{"", []string{`*.pn?`}}}, nil},
-		{FileFilters{{"", []string{`*.pn;`}}}, []string{"", "pn;"}},
-		{FileFilters{{"", []string{`*.pn\?`}}}, []string{"", "pn?"}},
-		{FileFilters{{"", []string{`*.[PpNnGg]`}}}, nil},
-		{FileFilters{{"", []string{`*.[Pp][Nn][Gg]`}}}, []string{"", "PNG"}},
-		{FileFilters{{"", []string{`*.[Pp][\Nn][G\g]`}}}, []string{"", "PNG"}},
-		{FileFilters{{"", []string{`*.[PNG`}}}, []string{"", "[PNG"}},
-		{FileFilters{{"", []string{`*.]PNG`}}}, []string{"", "]PNG"}},
-		{FileFilters{{"", []string{`*.[[]PNG`}}}, []string{"", "[PNG"}},
-		{FileFilters{{"", []string{`*.[]]PNG`}}}, []string{"", "]PNG"}},
-		{FileFilters{{"", []string{`*.[\[]PNG`}}}, []string{"", "[PNG"}},
-		{FileFilters{{"", []string{`*.[\]]PNG`}}}, []string{"", "]PNG"}},
-		{FileFilters{{"", []string{`public.png`}}}, []string{"", "public.png"}},
-		{FileFilters{{"", []string{`-public-.png`}}}, []string{"", "png"}},
+		{[]string{``}, nil},
+		{[]string{`*.png`}, []string{"", "png"}},
+		{[]string{`*.pn?`}, nil},
+		{[]string{`*.pn;`}, []string{"", "pn;"}},
+		{[]string{`*.pn\?`}, []string{"", "pn?"}},
+		{[]string{`*.[PpNnGg]`}, nil},
+		{[]string{`*.[Pp][Nn][Gg]`}, []string{"", "PNG"}},
+		{[]string{`*.[Pp][\Nn][G\g]`}, []string{"", "PNG"}},
+		{[]string{`*.[PNG`}, []string{"", "[PNG"}},
+		{[]string{`*.]PNG`}, []string{"", "]PNG"}},
+		{[]string{`*.[[]PNG`}, []string{"", "[PNG"}},
+		{[]string{`*.[]]PNG`}, []string{"", "]PNG"}},
+		{[]string{`*.[\[]PNG`}, []string{"", "[PNG"}},
+		{[]string{`*.[\]]PNG`}, []string{"", "]PNG"}},
+		{[]string{`public.png`}, []string{"", "public.png"}},
+		{[]string{`-public-.png`}, []string{"", "png"}},
 	}
 	for i, tt := range tests {
-		if got := tt.data.types(); !reflect.DeepEqual(got, tt.want) {
+		filters := FileFilters{FileFilter{Patterns: tt.data}}
+		if got := filters.types(); !reflect.DeepEqual(got, tt.want) {
 			t.Errorf("FileFilters.types[%d] = %v; want %v", i, got, tt.want)
 		}
 	}
diff --git a/file_test.go b/file_test.go
index d1df66e..8b70656 100644
--- a/file_test.go
+++ b/file_test.go
@@ -20,9 +20,9 @@ func ExampleSelectFile() {
 	zenity.SelectFile(
 		zenity.Filename(defaultPath),
 		zenity.FileFilters{
-			{"Go files", []string{"*.go"}},
-			{"Web files", []string{"*.html", "*.js", "*.css"}},
-			{"Image files", []string{"*.png", "*.gif", "*.ico", "*.jpg", "*.webp"}},
+			{"Go files", []string{"*.go"}, true},
+			{"Web files", []string{"*.html", "*.js", "*.css"}, true},
+			{"Image files", []string{"*.png", "*.gif", "*.ico", "*.jpg", "*.webp"}, true},
 		})
 }
 
@@ -30,9 +30,9 @@ func ExampleSelectFileMultiple() {
 	zenity.SelectFileMultiple(
 		zenity.Filename(defaultPath),
 		zenity.FileFilters{
-			{"Go files", []string{"*.go"}},
-			{"Web files", []string{"*.html", "*.js", "*.css"}},
-			{"Image files", []string{"*.png", "*.gif", "*.ico", "*.jpg", "*.webp"}},
+			{"Go files", []string{"*.go"}, true},
+			{"Web files", []string{"*.html", "*.js", "*.css"}, true},
+			{"Image files", []string{"*.png", "*.gif", "*.ico", "*.jpg", "*.webp"}, true},
 		})
 }
 
@@ -41,9 +41,9 @@ func ExampleSelectFileSave() {
 		zenity.ConfirmOverwrite(),
 		zenity.Filename(defaultName),
 		zenity.FileFilters{
-			{"Go files", []string{"*.go"}},
-			{"Web files", []string{"*.html", "*.js", "*.css"}},
-			{"Image files", []string{"*.png", "*.gif", "*.ico", "*.jpg", "*.webp"}},
+			{"Go files", []string{"*.go"}, true},
+			{"Web files", []string{"*.html", "*.js", "*.css"}, true},
+			{"Image files", []string{"*.png", "*.gif", "*.ico", "*.jpg", "*.webp"}, true},
 		})
 }
 
@@ -232,7 +232,7 @@ func TestSelectFileSave_script(t *testing.T) {
 		str, err := zenity.SelectFileSave(
 			zenity.ConfirmOverwrite(),
 			zenity.Filename("Χρτο.go"),
-			zenity.FileFilter{"Go files", []string{"*.go"}},
+			zenity.FileFilter{"Go files", []string{"*.go"}, true},
 		)
 		if skip, err := skip(err); skip {
 			t.Skip("skipping:", err)
diff --git a/file_windows.go b/file_windows.go
index 4dc2a2c..4fce08d 100644
--- a/file_windows.go
+++ b/file_windows.go
@@ -340,6 +340,9 @@ func initFilters(filters FileFilters) []uint16 {
 	filters.name()
 	var res []uint16
 	for _, f := range filters {
+		if f.Name == "" || len(f.Patterns) == 0 {
+			continue
+		}
 		res = append(res, utf16.Encode([]rune(f.Name))...)
 		res = append(res, 0)
 		for _, p := range f.Patterns {
diff --git a/zenity_test.go b/zenity_test.go
index 20802d1..de905d1 100644
--- a/zenity_test.go
+++ b/zenity_test.go
@@ -56,11 +56,11 @@ func Test_applyOptions(t *testing.T) {
 		{name: "ConfirmCreate", args: ConfirmCreate(), want: options{confirmCreate: true}},
 		{name: "ShowHidden", args: ShowHidden(), want: options{showHidden: true}},
 		{name: "Filename", args: Filename("file.go"), want: options{filename: "file.go"}},
-		{name: "FileFilter", args: FileFilter{"Go files", []string{"*.go"}}, want: options{
-			fileFilters: FileFilters{{"Go files", []string{"*.go"}}},
+		{name: "FileFilter", args: FileFilter{"Go files", []string{"*.go"}, true}, want: options{
+			fileFilters: FileFilters{{"Go files", []string{"*.go"}, true}},
 		}},
-		{name: "FileFilters", args: FileFilters{{"Go files", []string{"*.go"}}}, want: options{
-			fileFilters: FileFilters{{"Go files", []string{"*.go"}}},
+		{name: "FileFilters", args: FileFilters{{"Go files", []string{"*.go"}, true}}, want: options{
+			fileFilters: FileFilters{{"Go files", []string{"*.go"}, true}},
 		}},
 
 		// Color selection options