1 files changed, 2 insertions, 2 deletions
diff --git a/filter.c b/filter.c
index fa846483..4e77ebe3 100644
--- a/filter.c
+++ b/filter.c
@@ -292,10 +292,10 @@ static val trie_filter_string(val filter, val str)
     }
 
     if (match) {
-      string_extend(out, subst);
+      string_extend(out, subst, nil);
       i = plus(match, one);
     } else {
-      string_extend(out, chr_str(str, i));
+      string_extend(out, chr_str(str, i), nil);
       i = plus(i, one);
     }
   }