diff --git a/cpu/arm7_common/Makefile.include b/cpu/arm7_common/Makefile.include
index b31c843b6e..1c3447e340 100644
--- a/cpu/arm7_common/Makefile.include
+++ b/cpu/arm7_common/Makefile.include
@@ -18,4 +18,4 @@ LINKFLAGS   += -T$(RIOTCPU)/$(CPU)/ldscripts/$(CPU).ld
 LINKFLAGS   += $(CFLAGS_CPU) $(CFLAGS_DBG) $(CFLAGS_OPT) -static -lgcc -nostartfiles
 LINKFLAGS   += -Wl,--gc-sections
 
-export UNDEF += $(BINDIR)/cpu/startup.o
+UNDEF += $(BINDIR)/cpu/startup.o
diff --git a/cpu/kinetis/Makefile.include b/cpu/kinetis/Makefile.include
index a7778b2ec9..5947087209 100644
--- a/cpu/kinetis/Makefile.include
+++ b/cpu/kinetis/Makefile.include
@@ -44,7 +44,7 @@ CFLAGS += \
   #
 
 # add the CPU specific flash configuration field for the linker
-export UNDEF += $(BINDIR)/cpu/fcfield.o
+UNDEF += $(BINDIR)/cpu/fcfield.o
 
 # select kinetis periph drivers
 ifeq (EA,$(KINETIS_SERIES))
diff --git a/cpu/msp430_common/Makefile.include b/cpu/msp430_common/Makefile.include
index 84999be22e..b807ff2eb6 100644
--- a/cpu/msp430_common/Makefile.include
+++ b/cpu/msp430_common/Makefile.include
@@ -4,7 +4,7 @@ INCLUDES += -I$(RIOTCPU)/msp430_common/include/
 
 CFLAGS += -DCPU_MODEL_$(call uppercase_and_underscore,$(CPU_MODEL))
 
-export UNDEF += $(BINDIR)/msp430_common/startup.o
+UNDEF += $(BINDIR)/msp430_common/startup.o
 
 # include the msp430 common Makefile
 include $(RIOTMAKE)/arch/msp430.inc.mk