diff --git a/config.h.in b/config.h.in
index e27fa33..39b59f8 100644
--- a/config.h.in
+++ b/config.h.in
@@ -18,7 +18,8 @@
 /* Define to 1 if you have the <inttypes.h> header file. */
 #undef HAVE_INTTYPES_H
 
-/* Define to 1 if your system has a working `malloc' function. */
+/* Define to 1 if your system has a GNU libc compatible `malloc' function, and
+   to 0 otherwise. */
 #undef HAVE_MALLOC
 
 /* Define to 1 if you have the <memory.h> header file. */
@@ -114,6 +115,9 @@
 /* Define to empty if `const' does not conform to ANSI C. */
 #undef const
 
+/* Define to rpl_malloc if the replacement function should be used. */
+#undef malloc
+
 /* Define to `int' if <sys/types.h> does not define. */
 #undef mode_t