diff --git a/rules.mk b/rules.mk
index 2e4fce518..7a40d1de9 100644
--- a/rules.mk
+++ b/rules.mk
@@ -340,7 +340,8 @@ LST = $(patsubst %.c,$(OBJDIR)/%.lst,$(patsubst %.cpp,$(OBJDIR)/%.lst,$(patsubst
 
 
 # Compiler flags to generate dependency files.
-GENDEPFLAGS = -MMD -MP -MF .dep/$(@F).d
+#GENDEPFLAGS = -MMD -MP -MF .dep/$(@F).d
+GENDEPFLAGS = -MMD -MP -MF .dep/$(subst /,_,$@).d
 
 
 # Combine all necessary flags and optional flags.