diff --git a/config.h.in b/config.h.in
index b586808a..f9155955 100644
--- a/config.h.in
+++ b/config.h.in
@@ -6,18 +6,6 @@
 /* Define to 1 if you have the <byteswap.h> header file. */
 #undef HAVE_BYTESWAP_H
 
-/* Define to 1 if you have the declaration of `__bswap_constant_16', and to 0
-   if you don't. */
-#undef HAVE_DECL___BSWAP_CONSTANT_16
-
-/* Define to 1 if you have the declaration of `__bswap_constant_32', and to 0
-   if you don't. */
-#undef HAVE_DECL___BSWAP_CONSTANT_32
-
-/* Define to 1 if you have the declaration of `__bswap_constant_64', and to 0
-   if you don't. */
-#undef HAVE_DECL___BSWAP_CONSTANT_64
-
 /* Define to 1 if you have the <dlfcn.h> header file. */
 #undef HAVE_DLFCN_H