diff --git a/lib/vauth/digest.c b/lib/vauth/digest.c
index b7a0d92a31..fda2d911f7 100644
--- a/lib/vauth/digest.c
+++ b/lib/vauth/digest.c
@@ -694,6 +694,7 @@ static CURLcode auth_create_digest_http_message(
   char *hashthis = NULL;
   char *tmp = NULL;
 
+  memset(hashbuf, 0, sizeof(hashbuf));
   if(!digest->nc)
     digest->nc = 1;