diff -r 022fbd4bc057 -r 19379743e5a0 src/list.c
--- a/src/list.c	Sun Apr 09 19:37:00 2023 +0200
+++ b/src/list.c	Sun Apr 09 20:00:44 2023 +0200
@@ -219,11 +219,11 @@
         CxList const *list,
         CxList const *other
 ) {
-    if (list->cl->compare == other->cl->compare) {
-        // same compare function, lists are compatible
-        return list->cl->compare(list, other);
-    } else {
-        // different compare functions, use iterator
+    if ((list->store_pointer ^ other->store_pointer) ||
+        ((list->climpl == NULL) ^ (other->climpl != NULL)) ||
+        ((list->climpl != NULL ? list->climpl->compare : list->cl->compare) !=
+         (other->climpl != NULL ? other->climpl->compare : other->cl->compare))) {
+        // lists are definitely different - cannot use internal compare function
         if (list->size == other->size) {
             CxIterator left = cxListIterator(list);
             CxIterator right = cxListIterator(other);
@@ -241,6 +241,9 @@
         } else {
             return list->size < other->size ? -1 : 1;
         }
+    } else {
+        // lists are compatible
+        return list->cl->compare(list, other);
     }
 }