diff --git a/src/stransport_stream.c b/src/stransport_stream.c
index 66be58a21..008bdfb3c 100644
--- a/src/stransport_stream.c
+++ b/src/stransport_stream.c
@@ -67,6 +67,9 @@ int stransport_connect(git_stream *stream)
 	if ((ret = SSLCopyPeerTrust(st->ctx, &trust)) != noErr)
 		goto on_error;
 
+	if (!trust)
+		return GIT_ECERTIFICATE;
+
 	if ((ret = SecTrustEvaluate(trust, &sec_res)) != noErr)
 		goto on_error;