diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 8b8af166959..fdfb7806b39 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,9 @@
+2007-07-05  Joerg Richter  <joerg.richter@pdv-fs.de>
+
+	PR libstdc++/31957
+	* include/Makefile.am: Work around an AIX sed oddity.
+	* include/Makefile.in: Regenerate.
+	
 2007-07-04  Jim Xochellis  <jimxoch@yahoo.gr>
 
 	* include/bits/stl_algo.h (search(_ForwardIterator1,
diff --git a/libstdc++-v3/include/Makefile.am b/libstdc++-v3/include/Makefile.am
index 406b3130755..f661ed4fe07 100644
--- a/libstdc++-v3/include/Makefile.am
+++ b/libstdc++-v3/include/Makefile.am
@@ -1017,6 +1017,8 @@ stamp-visibility:
 	echo 0 > stamp-visibility
 endif
 
+# NB: The non-empty default ldbl_compat works around an AIX sed
+# oddity, see libstdc++/31957 for details.
 ${host_builddir}/c++config.h: ${CONFIG_HEADER} \
 			      ${glibcxx_srcdir}/include/bits/c++config \
 			      stamp-${host_alias} \
@@ -1026,7 +1028,7 @@ ${host_builddir}/c++config.h: ${CONFIG_HEADER} \
 	@date=`cat ${toplevel_srcdir}/gcc/DATESTAMP` ;\
 	nsa_version=`cat stamp-namespace-version` ;\
 	visibility=`cat stamp-visibility` ;\
-	ldbl_compat='' ;\
+	ldbl_compat='s,g,g,' ;\
 	grep "^[ 	]*#[ 	]*define[ 	][ 	]*_GLIBCXX_LONG_DOUBLE_COMPAT[ 	][ 	]*1[ 	]*$$" \
 	${CONFIG_HEADER} > /dev/null 2>&1 \
 	&& ldbl_compat='s,^#undef _GLIBCXX_LONG_DOUBLE_COMPAT$$,#define _GLIBCXX_LONG_DOUBLE_COMPAT 1,' ;\
diff --git a/libstdc++-v3/include/Makefile.in b/libstdc++-v3/include/Makefile.in
index bffba8da261..9f5c7fb681f 100644
--- a/libstdc++-v3/include/Makefile.in
+++ b/libstdc++-v3/include/Makefile.in
@@ -1404,6 +1404,8 @@ stamp-host: ${host_headers} ${host_headers_noinst} stamp-${host_alias}
 @ENABLE_VISIBILITY_FALSE@stamp-visibility:
 @ENABLE_VISIBILITY_FALSE@	echo 0 > stamp-visibility
 
+# NB: The non-empty default ldbl_compat works around an AIX sed
+# oddity, see libstdc++/31957 for details.
 ${host_builddir}/c++config.h: ${CONFIG_HEADER} \
 			      ${glibcxx_srcdir}/include/bits/c++config \
 			      stamp-${host_alias} \
@@ -1413,7 +1415,7 @@ ${host_builddir}/c++config.h: ${CONFIG_HEADER} \
 	@date=`cat ${toplevel_srcdir}/gcc/DATESTAMP` ;\
 	nsa_version=`cat stamp-namespace-version` ;\
 	visibility=`cat stamp-visibility` ;\
-	ldbl_compat='' ;\
+	ldbl_compat='s,g,g,' ;\
 	grep "^[ 	]*#[ 	]*define[ 	][ 	]*_GLIBCXX_LONG_DOUBLE_COMPAT[ 	][ 	]*1[ 	]*$$" \
 	${CONFIG_HEADER} > /dev/null 2>&1 \
 	&& ldbl_compat='s,^#undef _GLIBCXX_LONG_DOUBLE_COMPAT$$,#define _GLIBCXX_LONG_DOUBLE_COMPAT 1,' ;\