diff --git a/libidu/idu-hash.c b/libidu/idu-hash.c
index ec82a2b..b97400b 100644
--- a/libidu/idu-hash.c
+++ b/libidu/idu-hash.c
@@ -89,7 +89,7 @@ hash_find_slot (struct hash_table* ht, void const *key)
   ht->ht_lookups++;
   for (;;)
     {
-      hash_1 %= ht->ht_size;
+      hash_1 &= (ht->ht_size - 1);
       slot = &ht->ht_vec[hash_1];
 
       if (*slot == 0)