--- a/src/cx/map.h	Sun Oct 26 12:01:28 2025 +0100
+++ b/src/cx/map.h	Sun Oct 26 12:44:33 2025 +0100
@@ -528,7 +528,8 @@
  * Clones entries of a map if their key is not present in a list.
  *
  * Note that the list must contain keys of type @c CxKey
- * (or pointers to such keys).
+ * (or pointers to such keys) and must use @c cx_hash_key_cmp
+ * as the compare function.
  * Generic key types cannot be processed in this case.
  *
  * @param dst the destination map