diff --git a/AFNetworking/AFURLConnectionOperation.m b/AFNetworking/AFURLConnectionOperation.m
index cceb306..114cec2 100644
--- a/AFNetworking/AFURLConnectionOperation.m
+++ b/AFNetworking/AFURLConnectionOperation.m
@@ -335,6 +335,8 @@ didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
             
             if (credential) {
                 [[challenge sender] useCredential:credential forAuthenticationChallenge:challenge];
+            } else {
+                [[challenge sender] continueWithoutCredentialForAuthenticationChallenge:challenge];
             }
         } else {
             [[challenge sender] continueWithoutCredentialForAuthenticationChallenge:challenge];