diff --git a/lib/bitset.c b/lib/bitset.c
index f8249b8c..32521377 100644
--- a/lib/bitset.c
+++ b/lib/bitset.c
@@ -353,7 +353,7 @@ bitset_count_ (bitset src)
   {
     bitset_bindex next = 0;
     bitset_bindex num;
-    while (num = bitset_list (src, list, BITSET_LIST_SIZE, &next))
+    while ((num = bitset_list (src, list, BITSET_LIST_SIZE, &next)))
       count += num;
   }