diff --git a/Makefile b/Makefile
index 4d4b98e..9f9bee0 100644
--- a/Makefile
+++ b/Makefile
@@ -188,6 +188,10 @@ clean: libfdt_clean tests_clean
 	@$(VECHO) DEP $<
 	$(CC) $(CPPFLAGS) -MM -MG -MT "$*.o $@" $< > $@
 
+%.d: %.S
+	@$(VECHO) DEP $<
+	$(CC) $(CPPFLAGS) -MM -MG -MT "$*.o $@" $< > $@
+
 %.i:	%.c
 	@$(VECHO) CPP $@
 	$(CC) $(CPPFLAGS) -E $< > $@
diff --git a/tests/Makefile.tests b/tests/Makefile.tests
index 8ee0e5d..ec589aa 100644
--- a/tests/Makefile.tests
+++ b/tests/Makefile.tests
@@ -21,7 +21,8 @@ TESTS_TREES = $(TESTS_TREES_L:%=$(TESTS_PREFIX)%)
 
 TESTS_TARGETS = $(TESTS) $(TESTS_TREES)
 
-TESTS_DEPFILES = $(TESTS:%=%.d) $(TESTS_PREFIX)testutils.d
+TESTS_DEPFILES = $(TESTS:%=%.d) \
+	$(addprefix $(TESTS_PREFIX),testutils.d trees.d dumptrees.d)
 
 TESTS_CLEANFILES_L =  *.output vgcore.* *.dtb *.test.dts
 TESTS_CLEANFILES = $(TESTS_CLEANFILES_L:%=$(TESTS_PREFIX)%)