diff --git a/src/encoding/xml/xml.go b/src/encoding/xml/xml.go
index 384d6ad4b8..c902f1295a 100644
--- a/src/encoding/xml/xml.go
+++ b/src/encoding/xml/xml.go
@@ -1156,8 +1156,9 @@ func (d *Decoder) nsname() (name Name, ok bool) {
 	if !ok {
 		return
 	}
-	i := strings.Index(s, ":")
-	if i < 0 {
+	if strings.Count(s, ":") > 1 {
+		name.Local = s
+	} else if i := strings.Index(s, ":"); i < 1 || i > len(s)-2 {
 		name.Local = s
 	} else {
 		name.Space = s[0:i]
diff --git a/src/encoding/xml/xml_test.go b/src/encoding/xml/xml_test.go
index 5a10f5309d..47d0c39167 100644
--- a/src/encoding/xml/xml_test.go
+++ b/src/encoding/xml/xml_test.go
@@ -1003,3 +1003,59 @@ func TestTokenUnmarshaler(t *testing.T) {
 	d := NewTokenDecoder(tokReader{})
 	d.Decode(&Failure{})
 }
+
+func testRoundTrip(t *testing.T, input string) {
+	d := NewDecoder(strings.NewReader(input))
+	var tokens []Token
+	var buf bytes.Buffer
+	e := NewEncoder(&buf)
+	for {
+		tok, err := d.Token()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("invalid input: %v", err)
+		}
+		if err := e.EncodeToken(tok); err != nil {
+			t.Fatalf("failed to re-encode input: %v", err)
+		}
+		tokens = append(tokens, CopyToken(tok))
+	}
+	if err := e.Flush(); err != nil {
+		t.Fatal(err)
+	}
+
+	d = NewDecoder(&buf)
+	for {
+		tok, err := d.Token()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("failed to decode output: %v", err)
+		}
+		if len(tokens) == 0 {
+			t.Fatalf("unexpected token: %#v", tok)
+		}
+		a, b := tokens[0], tok
+		if !reflect.DeepEqual(a, b) {
+			t.Fatalf("token mismatch: %#v vs %#v", a, b)
+		}
+		tokens = tokens[1:]
+	}
+	if len(tokens) > 0 {
+		t.Fatalf("lost tokens: %#v", tokens)
+	}
+}
+
+func TestRoundTrip(t *testing.T) {
+	tests := map[string]string{
+		"leading colon":  `<::Test ::foo="bar"><:::Hello></:::Hello><Hello></Hello></::Test>`,
+		"trailing colon": `<foo abc:="x"></foo>`,
+		"double colon":   `<x:y:foo></x:y:foo>`,
+	}
+	for name, input := range tests {
+		t.Run(name, func(t *testing.T) { testRoundTrip(t, input) })
+	}
+}