diff --git a/lib/hx509/req.c b/lib/hx509/req.c
index 208d71f20..d0bfe91a9 100644
--- a/lib/hx509/req.c
+++ b/lib/hx509/req.c
@@ -669,6 +669,8 @@ hx509_request_to_pkcs10(hx509_context context,
         Attribute *a = NULL; /* Quiet VC */
         heim_any extns;
 
+        extns.data = NULL;
+        extns.length = 0;
         r.certificationRequestInfo.attributes =
             calloc(1, sizeof(r.certificationRequestInfo.attributes[0]));
         if (r.certificationRequestInfo.attributes == NULL)