diff --git a/oauthproxy.go b/oauthproxy.go
index 1dbb063..561dce3 100644
--- a/oauthproxy.go
+++ b/oauthproxy.go
@@ -204,7 +204,7 @@ func NewOAuthProxy(opts *Options, validator func(string) bool) *OAuthProxy {
 	}
 
 	redirectURL := opts.redirectURL
-	if redirectURL.String() == "" {
+	if redirectURL.Path == "" {
 		redirectURL.Path = fmt.Sprintf("%s/callback", opts.ProxyPrefix)
 	}