diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index 5c1708c..f9d9f44 100644
--- a/src/net/http/transport.go
+++ b/src/net/http/transport.go
@@ -710,6 +710,8 @@
 }
 
 func (t *Transport) connectMethodForRequest(treq *transportRequest) (cm connectMethod, err error) {
+	// TODO: the validPort check is redundant after CL 189258, as url.URL.Port
+	// only returns valid ports now. golang.org/issue/33600
 	if port := treq.URL.Port(); !validPort(port) {
 		return cm, fmt.Errorf("invalid URL port %q", port)
 	}
diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
index ea01a20..1a6f631 100644
--- a/src/net/http/transport_test.go
+++ b/src/net/http/transport_test.go
@@ -4289,7 +4289,7 @@
 		t.Fatalf("got %#v; want *url.Error", err)
 	}
 	got := ue.Err.Error()
-	want := `invalid URL port "123foo"`
+	want := `invalid port ":123foo" after host`
 	if got != want {
 		t.Errorf("got error %q; want %q", got, want)
 	}
diff --git a/src/net/url/url.go b/src/net/url/url.go
index 982cfe6..12ea35f 100644
--- a/src/net/url/url.go
+++ b/src/net/url/url.go
@@ -648,6 +648,11 @@
 			}
 			return host1 + host2 + host3, nil
 		}
+	} else if i := strings.LastIndex(host, ":"); i != -1 {
+		colonPort := host[i:]
+		if !validOptionalPort(colonPort) {
+			return "", fmt.Errorf("invalid port %q after host", colonPort)
+		}
 	}
 
 	var err error
@@ -1046,44 +1051,39 @@
 	return result
 }
 
-// Hostname returns u.Host, without any port number.
+// Hostname returns u.Host, stripping any valid port number if present.
 //
-// If Host is an IPv6 literal with a port number, Hostname returns the
-// IPv6 literal without the square brackets. IPv6 literals may include
-// a zone identifier.
+// If the result is enclosed in square brackets, as literal IPv6 addresses are,
+// the square brackets are removed from the result.
 func (u *URL) Hostname() string {
-	return stripPort(u.Host)
+	host, _ := splitHostPort(u.Host)
+	return host
 }
 
 // Port returns the port part of u.Host, without the leading colon.
-// If u.Host doesn't contain a port, Port returns an empty string.
+//
+// If u.Host doesn't contain a valid numeric port, Port returns an empty string.
 func (u *URL) Port() string {
-	return portOnly(u.Host)
+	_, port := splitHostPort(u.Host)
+	return port
 }
 
-func stripPort(hostport string) string {
-	colon := strings.IndexByte(hostport, ':')
-	if colon == -1 {
-		return hostport
-	}
-	if i := strings.IndexByte(hostport, ']'); i != -1 {
-		return strings.TrimPrefix(hostport[:i], "[")
-	}
-	return hostport[:colon]
-}
+// splitHostPort separates host and port. If the port is not valid, it returns
+// the entire input as host, and it doesn't check the validity of the host.
+// Unlike net.SplitHostPort, but per RFC 3986, it requires ports to be numeric.
+func splitHostPort(hostport string) (host, port string) {
+	host = hostport
 
-func portOnly(hostport string) string {
-	colon := strings.IndexByte(hostport, ':')
-	if colon == -1 {
-		return ""
+	colon := strings.LastIndexByte(host, ':')
+	if colon != -1 && validOptionalPort(host[colon:]) {
+		host, port = host[:colon], host[colon+1:]
 	}
-	if i := strings.Index(hostport, "]:"); i != -1 {
-		return hostport[i+len("]:"):]
+
+	if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") {
+		host = host[1 : len(host)-1]
 	}
-	if strings.Contains(hostport, "]") {
-		return ""
-	}
-	return hostport[colon+len(":"):]
+
+	return
 }
 
 // Marshaling interface implementations.
diff --git a/src/net/url/url_test.go b/src/net/url/url_test.go
index e6d6ef8..e83c86c 100644
--- a/src/net/url/url_test.go
+++ b/src/net/url/url_test.go
@@ -422,10 +422,10 @@
 	},
 	// worst case host, still round trips
 	{
-		"scheme://!$&'()*+,;=hello!:port/path",
+		"scheme://!$&'()*+,;=hello!:1/path",
 		&URL{
 			Scheme: "scheme",
-			Host:   "!$&'()*+,;=hello!:port",
+			Host:   "!$&'()*+,;=hello!:1",
 			Path:   "/path",
 		},
 		"",
@@ -1425,11 +1425,13 @@
 		{"http://[::1]", false},
 		{"http://[::1]:80", false},
 		{"http://[::1]:namedport", true}, // rfc3986 3.2.3
+		{"http://x:namedport", true},     // rfc3986 3.2.3
 		{"http://[::1]/", false},
 		{"http://[::1]a", true},
 		{"http://[::1]%23", true},
 		{"http://[::1%25en0]", false},     // valid zone id
 		{"http://[::1]:", false},          // colon, but no port OK
+		{"http://x:", false},              // colon, but no port OK
 		{"http://[::1]:%38%30", true},     // not allowed: % encoding only for non-ASCII
 		{"http://[::1%25%41]", false},     // RFC 6874 allows over-escaping in zone
 		{"http://[%10::1]", true},         // no %xx escapes in IP address
@@ -1621,52 +1623,46 @@
 	}
 }
 
-func TestURLHostname(t *testing.T) {
+func TestURLHostnameAndPort(t *testing.T) {
 	tests := []struct {
-		host string // URL.Host field
-		want string
+		in   string // URL.Host field
+		host string
+		port string
 	}{
-		{"foo.com:80", "foo.com"},
-		{"foo.com", "foo.com"},
-		{"FOO.COM", "FOO.COM"}, // no canonicalization (yet?)
-		{"1.2.3.4", "1.2.3.4"},
-		{"1.2.3.4:80", "1.2.3.4"},
-		{"[1:2:3:4]", "1:2:3:4"},
-		{"[1:2:3:4]:80", "1:2:3:4"},
-		{"[::1]:80", "::1"},
-		{"[::1]", "::1"},
-		{"localhost", "localhost"},
-		{"localhost:443", "localhost"},
-		{"some.super.long.domain.example.org:8080", "some.super.long.domain.example.org"},
-		{"[2001:0db8:85a3:0000:0000:8a2e:0370:7334]:17000", "2001:0db8:85a3:0000:0000:8a2e:0370:7334"},
-		{"[2001:0db8:85a3:0000:0000:8a2e:0370:7334]", "2001:0db8:85a3:0000:0000:8a2e:0370:7334"},
-	}
-	for _, tt := range tests {
-		u := &URL{Host: tt.host}
-		got := u.Hostname()
-		if got != tt.want {
-			t.Errorf("Hostname for Host %q = %q; want %q", tt.host, got, tt.want)
-		}
-	}
-}
+		{"foo.com:80", "foo.com", "80"},
+		{"foo.com", "foo.com", ""},
+		{"foo.com:", "foo.com", ""},
+		{"FOO.COM", "FOO.COM", ""}, // no canonicalization
+		{"1.2.3.4", "1.2.3.4", ""},
+		{"1.2.3.4:80", "1.2.3.4", "80"},
+		{"[1:2:3:4]", "1:2:3:4", ""},
+		{"[1:2:3:4]:80", "1:2:3:4", "80"},
+		{"[::1]:80", "::1", "80"},
+		{"[::1]", "::1", ""},
+		{"[::1]:", "::1", ""},
+		{"localhost", "localhost", ""},
+		{"localhost:443", "localhost", "443"},
+		{"some.super.long.domain.example.org:8080", "some.super.long.domain.example.org", "8080"},
+		{"[2001:0db8:85a3:0000:0000:8a2e:0370:7334]:17000", "2001:0db8:85a3:0000:0000:8a2e:0370:7334", "17000"},
+		{"[2001:0db8:85a3:0000:0000:8a2e:0370:7334]", "2001:0db8:85a3:0000:0000:8a2e:0370:7334", ""},
 
-func TestURLPort(t *testing.T) {
-	tests := []struct {
-		host string // URL.Host field
-		want string
-	}{
-		{"foo.com", ""},
-		{"foo.com:80", "80"},
-		{"1.2.3.4", ""},
-		{"1.2.3.4:80", "80"},
-		{"[1:2:3:4]", ""},
-		{"[1:2:3:4]:80", "80"},
+		// Ensure that even when not valid, Host is one of "Hostname",
+		// "Hostname:Port", "[Hostname]" or "[Hostname]:Port".
+		// See https://golang.org/issue/29098.
+		{"[google.com]:80", "google.com", "80"},
+		{"google.com]:80", "google.com]", "80"},
+		{"google.com:80_invalid_port", "google.com:80_invalid_port", ""},
+		{"[::1]extra]:80", "::1]extra", "80"},
+		{"google.com]extra:extra", "google.com]extra:extra", ""},
 	}
 	for _, tt := range tests {
-		u := &URL{Host: tt.host}
-		got := u.Port()
-		if got != tt.want {
-			t.Errorf("Port for Host %q = %q; want %q", tt.host, got, tt.want)
+		u := &URL{Host: tt.in}
+		host, port := u.Hostname(), u.Port()
+		if host != tt.host {
+			t.Errorf("Hostname for Host %q = %q; want %q", tt.in, host, tt.host)
+		}
+		if port != tt.port {
+			t.Errorf("Port for Host %q = %q; want %q", tt.in, port, tt.port)
 		}
 	}
 }