diff --git a/openbsc/tests/bsc-nat/Makefile.am b/openbsc/tests/bsc-nat/Makefile.am
index 9b71d09..0847678 100644
--- a/openbsc/tests/bsc-nat/Makefile.am
+++ b/openbsc/tests/bsc-nat/Makefile.am
@@ -1,4 +1,4 @@
-INCLUDES = $(all_includes) -I$(top_srcdir)/include
+AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include
 AM_CFLAGS=-Wall -ggdb3 $(LIBOSMOCORE_CFLAGS) $(LIBOSMOGSM_CFLAGS) $(LIBOSMOSCCP_CFLAGS) $(LIBOSMOABIS_CFLAGS) $(COVERAGE_CFLAGS)
 AM_LDFLAGS = $(COVERAGE_LDFLAGS)