remove warning
diff --git a/skeletons/OCTET_STRING_oer.c b/skeletons/OCTET_STRING_oer.c
index 9f878d1..7fa76c0 100644
--- a/skeletons/OCTET_STRING_oer.c
+++ b/skeletons/OCTET_STRING_oer.c
@@ -141,7 +141,7 @@
             break;
         }
 
-        if(st->size != unit_bytes * ct_size) {
+        if(st->size != unit_bytes * (size_t)ct_size) {
             ASN_DEBUG(
                 "Trying to encode %s (%zu bytes) which doesn't fit SIZE "
                 "constraint (%d)",