diff --git a/packages/Makefile b/packages/Makefile
index 90ab517fc7ff49025eb93a3352d2c2727f356aa2..6f7b7bb056b4246ec8df3bc0d0827d7d848c2f24 100644
--- a/packages/Makefile
+++ b/packages/Makefile
@@ -143,11 +143,11 @@ else
 #----------------------------------------------------------------------------#
 # old build system
 PD_AUTOCONF = autoconf
-$(pd_src)/src/configure: $(pd_src)/src/configure.in
+$(pd_src)/src/configure: $(pd_src)/src/configure.ac 
 	cd $(pd_src)/src/ && \
 	if [ -f acinclude.m4 ] ; then aclocal ; fi && \
 	$(PD_AUTOCONF) && \
-	if grep -q AC_CONFIG_HEADERS configure.in ; then autoheader ; fi
+	if grep -q AC_CONFIG_HEADERS configure.ac ; then autoheader ; fi 
 
 # this is not used yet because MinGW doesn't use ./configure && make yet
 #$(pd_src)/src/makefile: $(pd_src)/src/makefile.in