diff --git a/src/gcal-source-dialog.c b/src/gcal-source-dialog.c
index 5e1a99f0..5c269d1e 100644
--- a/src/gcal-source-dialog.c
+++ b/src/gcal-source-dialog.c
@@ -1194,6 +1194,7 @@ validate_url_cb (GcalSourceDialog *dialog)
           gchar *user, *password;
 
           response = prompt_credentials (dialog, &user, &password);
+          user = password = NULL;
 
           /*
            * User entered username and password, let's try