diff --git a/Makefile.in b/Makefile.in
index 4e20827b8..2fddfef84 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -145,7 +145,7 @@ conf:
 	cd $(srcdir) && $(MAKE) -f prepare-source.mak conf
 
 aclocal.m4: m4/*.m4
-	aclocal
+	aclocal -I $(srcdir)/m4
 
 configure.sh config.h.in: configure.ac aclocal.m4
 	@if test -f configure.sh; then cp -p configure.sh configure.sh.old; else touch configure.sh.old; fi
diff --git a/prepare-source.mak b/prepare-source.mak
index efb622839..ad291feb9 100644
--- a/prepare-source.mak
+++ b/prepare-source.mak
@@ -1,7 +1,7 @@
 conf: configure.sh config.h.in
 
 aclocal.m4:
-	aclocal
+	aclocal -I m4
 
 configure.sh: configure.ac aclocal.m4
 	autoconf -o configure.sh