diff --git a/include/curl/curl.h b/include/curl/curl.h
index 5b4ae469e..9481aca8c 100644
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@@ -479,7 +479,7 @@ typedef enum {
   CURLE_LDAP_CANNOT_BIND,        /* 38 */
   CURLE_LDAP_SEARCH_FAILED,      /* 39 */
   CURLE_OBSOLETE40,              /* 40 - NOT USED */
-  CURLE_FUNCTION_NOT_FOUND,      /* 41 */
+  CURLE_FUNCTION_NOT_FOUND,      /* 41 - NOT USED starting with 7.52.2 */
   CURLE_ABORTED_BY_CALLBACK,     /* 42 */
   CURLE_BAD_FUNCTION_ARGUMENT,   /* 43 */
   CURLE_OBSOLETE44,              /* 44 - NOT USED */