diff --git a/src/mime/mediatype.go b/src/mime/mediatype.go
index ad63f9bb98e9a4..00076048a1578b 100644
--- a/src/mime/mediatype.go
+++ b/src/mime/mediatype.go
@@ -237,24 +237,23 @@ func consumeToken(v string) (token, rest string) {
 // quoted-string) and the rest of the string.  On failure, returns
 // ("", v).
 func consumeValue(v string) (value, rest string) {
-	if !strings.HasPrefix(v, `"`) && !strings.HasPrefix(v, `'`) {
+	if v == "" {
+		return
+	}
+	if v[0] != '"' {
 		return consumeToken(v)
 	}
 
-	leadQuote := rune(v[0])
-
 	// parse a quoted-string
 	rest = v[1:] // consume the leading quote
 	buffer := new(bytes.Buffer)
-	var idx int
-	var r rune
 	var nextIsLiteral bool
-	for idx, r = range rest {
+	for idx, r := range rest {
 		switch {
 		case nextIsLiteral:
 			buffer.WriteRune(r)
 			nextIsLiteral = false
-		case r == leadQuote:
+		case r == '"':
 			return buffer.String(), rest[idx+1:]
 		case r == '\\':
 			nextIsLiteral = true
diff --git a/src/mime/mediatype_test.go b/src/mime/mediatype_test.go
index 026bfa4d734681..e72f95f0a0338f 100644
--- a/src/mime/mediatype_test.go
+++ b/src/mime/mediatype_test.go
@@ -159,7 +159,7 @@ func TestParseMediaType(t *testing.T) {
 			m("filename", "foo.html")},
 		{`attachment; filename='foo.html'`,
 			"attachment",
-			m("filename", "foo.html")},
+			m("filename", "'foo.html'")},
 		{`attachment; filename="foo-%41.html"`,
 			"attachment",
 			m("filename", "foo-%41.html")},
@@ -294,6 +294,7 @@ var formatTests = []formatTest{
 	{"foo/BAR", map[string]string{"bad attribute": "baz"}, ""},
 	{"foo/BAR", map[string]string{"nonascii": "not an ascii character: ä"}, ""},
 	{"foo/bar", map[string]string{"a": "av", "b": "bv", "c": "cv"}, "foo/bar; a=av; b=bv; c=cv"},
+	{"foo/bar", map[string]string{"0": "'", "9": "'"}, "foo/bar; 0='; 9='"},
 }
 
 func TestFormatMediaType(t *testing.T) {