diff --git a/make_forward b/make_forward
index fe05f8af..8c535345 100644
--- a/make_forward
+++ b/make_forward
@@ -10,7 +10,9 @@ SICS_ROOT=$(PWD)/$(S_UP)
 OBJROOT=$(SICS_ROOT)/obj/$(SICS_VERSION)
 MD=cd $(OBJROOT)/$(S_DOWN); \
   make -f $(SRC)makefile_$(SICS_VERSION) SRC=$(SRC)
-TREE=$(OBJROOT)/tree
+
+#define TREE only when version defined
+TREE$(VERS_UNDEFINED)=$(OBJROOT)/tree
 
 # overwrite MD when SICS_VERSION undefined
 MD$(SICS_VERSION)=@ true
@@ -38,6 +40,7 @@ tree: $(TREE)
 	@ true
 
 $(TREE):
+	@ $(VERS_UNDEFINED)
 	@ echo --- Make object tree ---
 	@ $(SICS_ROOT)/maketree .
 	@ $(SICS_ROOT)/maketree matrix