diff --git a/openbsc/tests/smpp/Makefile.am b/openbsc/tests/smpp/Makefile.am
index aab4de9..5082707 100644
--- a/openbsc/tests/smpp/Makefile.am
+++ b/openbsc/tests/smpp/Makefile.am
@@ -1,13 +1,40 @@
-AM_CPPFLAGS = $(all_includes) -I$(top_srcdir)/include -I$(top_srcdir)/src/libmsc
-AM_CFLAGS=-Wall -ggdb3 $(LIBOSMOCORE_CFLAGS) $(LIBOSMOGSM_CFLAGS) $(LIBOSMOSCCP_CFLAGS) $(LIBOSMOABIS_CFLAGS) $(COVERAGE_CFLAGS) $(LIBSMPP34_CFLAGS)
-AM_LDFLAGS = $(COVERAGE_LDFLAGS)
+AM_CPPFLAGS = \
+	$(all_includes) \
+	-I$(top_srcdir)/include \
+	-I$(top_srcdir)/src/libmsc \
+	$(NULL)
 
-EXTRA_DIST = smpp_test.ok smpp_test.err
+AM_CFLAGS = \
+	-Wall \
+	-ggdb3 \
+	$(LIBOSMOCORE_CFLAGS) \
+	$(LIBOSMOGSM_CFLAGS) \
+	$(LIBOSMOSCCP_CFLAGS) \
+	$(LIBOSMOABIS_CFLAGS) \
+	$(COVERAGE_CFLAGS) \
+	$(LIBSMPP34_CFLAGS) \
+	$(NULL)
 
-noinst_PROGRAMS = smpp_test
+AM_LDFLAGS = \
+	$(COVERAGE_LDFLAGS) \
+	$(NULL)
 
-smpp_test_SOURCES = smpp_test.c \
-	$(top_builddir)/src/libmsc/smpp_utils.c
+EXTRA_DIST = \
+	smpp_test.ok \
+	smpp_test.err \
+	$(NULL)
+
+noinst_PROGRAMS = \
+	smpp_test \
+	$(NULL)
+
+smpp_test_SOURCES = \
+	smpp_test.c \
+	$(top_builddir)/src/libmsc/smpp_utils.c \
+	$(NULL)
+
 smpp_test_LDADD = \
 	$(top_builddir)/src/libcommon/libcommon.a \
-	$(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS)
+	$(LIBOSMOCORE_LIBS) \
+	$(LIBOSMOGSM_LIBS) \
+	$(NULL)