--- a/Makefile.am
+++ b/Makefile.am
@@ -1,5 +1,7 @@
 ## Process this file with automake to produce Makefile.in
 
+ACLOCAL_AMFLAGS = -I M4
+
 DISTCHECK_CONFIGURE_FLAGS = --enable-gcc-werror
 
 if BUILD_OCTAVE_MOD
