diff --git a/registry/client/auth/addr.go b/registry/client/auth/addr.go
new file mode 100644
index 00000000..6e777528
--- /dev/null
+++ b/registry/client/auth/addr.go
@@ -0,0 +1,27 @@
+package auth
+
+import (
+	"net/url"
+	"strings"
+)
+
+// FROM: https://golang.org/src/net/http/http.go
+// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
+// return true if the string includes a port.
+func hasPort(s string) bool { return strings.LastIndex(s, ":") > strings.LastIndex(s, "]") }
+
+// FROM: http://golang.org/src/net/http/transport.go
+var portMap = map[string]string{
+	"http":  "80",
+	"https": "443",
+}
+
+// canonicalAddr returns url.Host but always with a ":port" suffix
+// FROM: http://golang.org/src/net/http/transport.go
+func canonicalAddr(url *url.URL) string {
+	addr := url.Host
+	if !hasPort(addr) {
+		return addr + ":" + portMap[url.Scheme]
+	}
+	return addr
+}
diff --git a/registry/client/auth/authchallenge.go b/registry/client/auth/authchallenge.go
index e8cdef7f..69d9d6fe 100644
--- a/registry/client/auth/authchallenge.go
+++ b/registry/client/auth/authchallenge.go
@@ -54,8 +54,13 @@ type simpleChallengeManager struct {
 	Challanges map[string][]Challenge
 }
 
-func (m *simpleChallengeManager) GetChallenges(endpoint url.URL) ([]Challenge, error) {
+func normalizeURL(endpoint *url.URL) {
 	endpoint.Host = strings.ToLower(endpoint.Host)
+	endpoint.Host = canonicalAddr(endpoint)
+}
+
+func (m *simpleChallengeManager) GetChallenges(endpoint url.URL) ([]Challenge, error) {
+	normalizeURL(&endpoint)
 
 	m.RLock()
 	defer m.RUnlock()
@@ -70,9 +75,11 @@ func (m *simpleChallengeManager) AddResponse(resp *http.Response) error {
 	}
 	urlCopy := url.URL{
 		Path:   resp.Request.URL.Path,
-		Host:   strings.ToLower(resp.Request.URL.Host),
+		Host:   resp.Request.URL.Host,
 		Scheme: resp.Request.URL.Scheme,
 	}
+	normalizeURL(&urlCopy)
+
 	m.Lock()
 	defer m.Unlock()
 	m.Challanges[urlCopy.String()] = challenges
diff --git a/registry/client/auth/authchallenge_test.go b/registry/client/auth/authchallenge_test.go
index e767ed74..2716fba5 100644
--- a/registry/client/auth/authchallenge_test.go
+++ b/registry/client/auth/authchallenge_test.go
@@ -44,6 +44,7 @@ func TestAuthChallengeParse(t *testing.T) {
 func TestAuthChallengeNormalization(t *testing.T) {
 	testAuthChallengeNormalization(t, "reg.EXAMPLE.com")
 	testAuthChallengeNormalization(t, "bɿɒʜɔiɿ-ɿɘƚƨim-ƚol-ɒ-ƨʞnɒʜƚ.com")
+	testAuthChallengeNormalization(t, "reg.example.com:80")
 	testAuthChallengeConcurrent(t, "reg.EXAMPLE.com")
 }
 
@@ -72,6 +73,7 @@ func testAuthChallengeNormalization(t *testing.T, host string) {
 
 	lowered := *url
 	lowered.Host = strings.ToLower(lowered.Host)
+	lowered.Host = canonicalAddr(&lowered)
 	c, err := scm.GetChallenges(lowered)
 	if err != nil {
 		t.Fatal(err)