diff --git a/src/core/wee-url.c b/src/core/wee-url.c
index b0d19a340..d3a086b88 100644
--- a/src/core/wee-url.c
+++ b/src/core/wee-url.c
@@ -1027,7 +1027,7 @@ weeurl_search_constant (struct t_url_constant *constants, const char *name)
 {
     int i;
 
-    if (!name)
+    if (!constants || !name)
         return -1;
 
     for (i = 0; constants[i].name; i++)
@@ -1056,6 +1056,9 @@ weeurl_get_mask_value (struct t_url_constant *constants,
     int num_items, i, index;
     long mask;
 
+    if (!constants || !string_mask)
+        return 0;
+
     mask = 0;
 
     items = string_split (string_mask, "+", NULL,