diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index d3b0aae454a..44eaa18291b 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -660,7 +660,7 @@ _get_peer_alt_names (X509 *certificate) {
 	char buf[2048];
 	char *vptr;
 	int len;
-	unsigned char *p;
+	const unsigned char *p;
 
 	if (certificate == NULL)
 		return peer_alt_names;