diff --git a/make/rules.mk b/make/rules.mk
index 04ddf8c6..d6a936dd 100644
--- a/make/rules.mk
+++ b/make/rules.mk
@@ -187,8 +187,10 @@ endif
 #depend.mk: $(SRC_ALL_CPP)
 #	> $@ && makedepend -f depend.mk -- $(CPPFLAGS) $(DEPEND_CPPFLAGS) -- $(SRC_ALL_CPP) 2>&1 | sed '/non-portable whitespace/ d'
 
-depend.mk: $(SRC_ALL_CPP)
-	> $@ && gcc -M $(CPPFLAGS) $(DEPEND_CPPFLAGS) $(filter-out %.h,$(SRC_ALL_CPP)) -o $@
+depend.mk: $(filter-out %.h, $(SRC_ALL_CPP) $(PREREQ_DONE))
+	> $@ && if [ "$(wildcard *.cpp *.c)" ]; then \
+		gcc -M $(CPPFLAGS) $(DEPEND_CPPFLAGS) $(filter-out %.h,$(SRC_ALL_CPP)) -o $@; \
+	fi
 
 depend: depend.mk