diff --git a/http.c b/http.c
index c29ce81ccc..d20e9c108b 100644
--- a/http.c
+++ b/http.c
@@ -709,6 +709,8 @@ int start_active_slot(struct active_request_slot *slot)
 
 	if (curlm_result != CURLM_OK &&
 	    curlm_result != CURLM_CALL_MULTI_PERFORM) {
+		warning("curl_multi_add_handle failed: %s",
+			curl_multi_strerror(curlm_result));
 		active_requests--;
 		slot->in_use = 0;
 		return 0;