diff --git a/src/include/config.h.in b/src/include/config.h.in
index 9ec12b5d19..af032952ef 100644
--- a/src/include/config.h.in
+++ b/src/include/config.h.in
@@ -101,8 +101,8 @@
  * pgsql/src/backend/utils/fmgr/fmgr.c and add additional entries 
  * to the 'case' statement for the additional arguments.
  */
-#define INDEX_MAX_KEYS		16
-#define FUNC_MAX_ARGS		INDEX_MAX_KEYS
+#define INDEX_MAX_KEYS		8
+#define FUNC_MAX_ARGS		(INDEX_MAX_KEYS+1)
 
 /*
  * Enables debugging print statements in the date/time support routines.