diff --git a/src/modules/Gmp/configure.in b/src/modules/Gmp/configure.in
index 5f7095ff931533137fd4eef2203df2b48178d905..bf55658aeedd9c17abb4496399269c80d7fc7bf3 100644
--- a/src/modules/Gmp/configure.in
+++ b/src/modules/Gmp/configure.in
@@ -1,4 +1,4 @@
-# $Id: configure.in,v 1.27 2001/08/29 16:19:32 mast Exp $
+# $Id: configure.in,v 1.28 2001/09/25 00:55:59 hubbe Exp $
 AC_INIT(mpz_glue.c)
 AC_CONFIG_HEADER(gmp_machine.h)
 AC_ARG_WITH(gmp,     [  --with(out)-gmp        Support bignums],[],[with_gmp=yes])
@@ -84,7 +84,13 @@ __MPN(PiKe)
       AC_MSG_RESULT($PIKE_PREFIX_NAME)
       AC_DEFINE_UNQUOTED(PIKE_MPN_PREFIX, $PIKE_PREFIX_NAME)
     fi
-    undefine(PIKE_PREFIX_NAME)
+
+dnl 
+dnl  Autoconf 2.52 seems to barf on this undefine for
+dnl  some unknown reason. This file should work just
+dnl  as well without it.
+dnl
+dnl    undefine(PIKE_PREFIX_NAME)
 
     AC_MSG_CHECKING(working <$2>)
     AC_CACHE_VAL(pike_cv_working_$1,[
diff --git a/src/modules/_Image_XFace/configure.in b/src/modules/_Image_XFace/configure.in
index 22517bfa18253cafafb935ae42e938d443bba1bd..19a86a1fbc49830d57460848642ee00a857dc654 100755
--- a/src/modules/_Image_XFace/configure.in
+++ b/src/modules/_Image_XFace/configure.in
@@ -1,4 +1,4 @@
-# $Id: configure.in,v 1.8 2001/02/13 15:44:18 mirar Exp $
+# $Id: configure.in,v 1.9 2001/09/25 00:56:00 hubbe Exp $
 AC_INIT(image_xface.c)
 AC_CONFIG_HEADER(config.h)
 AC_ARG_WITH(gmp,     [  --with(out)-gmp        Support bignums],[],[with_gmp=yes])
@@ -79,7 +79,13 @@ __MPN(PiKe)
       AC_MSG_RESULT($PIKE_PREFIX_NAME)
       AC_DEFINE_UNQUOTED(PIKE_MPN_PREFIX, $PIKE_PREFIX_NAME)
     fi
-    undefine(PIKE_PREFIX_NAME)
+
+dnl 
+dnl  Autoconf 2.52 seems to barf on this undefine for
+dnl  some unknown reason. This file should work just
+dnl  as well without it.
+dnl
+dnl    undefine(PIKE_PREFIX_NAME)
 
     AC_MSG_CHECKING(working <$2>)
     AC_CACHE_VAL(pike_cv_working_$1,[