diff --git a/boards/native/Makefile.include b/boards/native/Makefile.include
index fdd510ead1..3974fbbc49 100644
--- a/boards/native/Makefile.include
+++ b/boards/native/Makefile.include
@@ -160,4 +160,4 @@ eval-gprof:
 eval-cachegrind:
 	$(CGANNOTATE) $(shell ls -rt cachegrind.out* | tail -1)
 
-export UNDEF += $(BINDIR)/cpu/startup.o
+UNDEF += $(BINDIR)/cpu/startup.o