diff --git a/src/net/url/url.go b/src/net/url/url.go
index a6975488014..6afa30f162b 100644
--- a/src/net/url/url.go
+++ b/src/net/url/url.go
@@ -698,9 +698,7 @@ func parseHost(host string) (string, error) {
 			return "", errors.New("invalid IP-literal")
 		}
 		return "[" + unescapedHostname + "]" + unescapedColonPort, nil
-	} else if i := strings.Index(host, ":"); i != -1 {
-		// IPv4address / reg-name
-		// E.g. 1.2.3.4, 1.2.3.4:80, example.com, example.com:80
+	} else if i := strings.LastIndex(host, ":"); i != -1 {
 		colonPort := host[i:]
 		if !validOptionalPort(colonPort) {
 			return "", fmt.Errorf("invalid port %q after host", colonPort)
diff --git a/src/net/url/url_test.go b/src/net/url/url_test.go
index a7543d6fd40..6084facacc0 100644
--- a/src/net/url/url_test.go
+++ b/src/net/url/url_test.go
@@ -506,6 +506,26 @@ var urltests = []URLTest{
 		},
 		"",
 	},
+	{
+		// Malformed IPv6 but still accepted.
+		"http://2b01:e34:ef40:7730:8e70:5aff:fefe:edac:8080/foo",
+		&URL{
+			Scheme: "http",
+			Host:   "2b01:e34:ef40:7730:8e70:5aff:fefe:edac:8080",
+			Path:   "/foo",
+		},
+		"",
+	},
+	{
+		// Malformed IPv6 but still accepted.
+		"http://2b01:e34:ef40:7730:8e70:5aff:fefe:edac:/foo",
+		&URL{
+			Scheme: "http",
+			Host:   "2b01:e34:ef40:7730:8e70:5aff:fefe:edac:",
+			Path:   "/foo",
+		},
+		"",
+	},
 	{
 		"http://[2b01:e34:ef40:7730:8e70:5aff:fefe:edac]:8080/foo",
 		&URL{
@@ -715,9 +735,6 @@ var parseRequestURLTests = []struct {
 	{"https://[0:0::test.com]:80", false},
 	{"https://[2001:db8::test.com]", false},
 	{"https://[test.com]", false},
-	{"https://1:2:3:4:5:6:7:8", false},
-	{"https://1:2:3:4:5:6:7:8:80", false},
-	{"https://example.com:80:", false},
 }
 
 func TestParseRequestURI(t *testing.T) {