--- a/src/cx/hash_key.h	Sun Oct 26 12:01:28 2025 +0100
+++ b/src/cx/hash_key.h	Sun Oct 26 12:44:33 2025 +0100
@@ -227,12 +227,14 @@
 /**
  * Compare function for hash keys.
  *
- * @param left the first key
- * @param right the second key
+ * The pointers are untyped to be compatible with the cx_compare_func signature.
+ *
+ * @param left (@c CxHashKey*) the first key
+ * @param right (@c CxHashKey*) the second key
  * @return zero when the keys equal, non-zero when they differ
  */
 cx_attr_nodiscard cx_attr_nonnull
-CX_EXPORT int cx_hash_key_cmp(const CxHashKey *left, const CxHashKey *right);
+CX_EXPORT int cx_hash_key_cmp(const void *left, const void *right);
 
 #ifdef __cplusplus
 } // extern "C"