diff --git a/autogen.sh b/autogen.sh
index b46d1e6c90a..65139b4194c 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -265,7 +265,8 @@ Please report any problems with this script to bug-gnu-emacs@gnu.org .'
 
   ## Let autoreconf figure out what, if anything, needs doing.
   ## Use autoreconf's -f option in case autoreconf itself has changed.
-  autoreconf -fi -I m4 || exit
+  ## Use absolute include path because autoreconf also runs in ./mps.
+  autoreconf -fi -I `pwd`/m4 || exit
 
   echo "Building 'aclocal.m4' in exec ..."