diff --git a/act/artifactcache/mac.go b/act/artifactcache/mac.go
index d41a76cf..1b129b77 100644
--- a/act/artifactcache/mac.go
+++ b/act/artifactcache/mac.go
@@ -45,7 +45,9 @@ func validateAge(ts string) bool {
 func computeMac(secret, repo, run, ts string) string {
 	mac := hmac.New(sha256.New, []byte(secret))
 	mac.Write([]byte(repo))
+	mac.Write([]byte(">"))
 	mac.Write([]byte(run))
+	mac.Write([]byte(">"))
 	mac.Write([]byte(ts))
 	return hex.EncodeToString(mac.Sum(nil))
 }
diff --git a/act/cacheproxy/handler.go b/act/cacheproxy/handler.go
index 293b2bc7..13997ef2 100644
--- a/act/cacheproxy/handler.go
+++ b/act/cacheproxy/handler.go
@@ -166,7 +166,7 @@ func (h *Handler) newReverseProxy(targetHost string) (*httputil.ReverseProxy, er
 
 func (h *Handler) ExternalURL() string {
 	// TODO: make the external url configurable if necessary
-	return net.JoinHostPort(h.outboundIP, strconv.Itoa(h.listener.Addr().(*net.TCPAddr).Port))
+	return fmt.Sprintf("http://%s", net.JoinHostPort(h.outboundIP, strconv.Itoa(h.listener.Addr().(*net.TCPAddr).Port)))
 }
 
 // Informs the proxy of a workflow run that can make cache requests.