diff --git a/cpu/mcf52x2/config.mk b/cpu/mcf52x2/config.mk
index f97157d041..c3899c507e 100644
--- a/cpu/mcf52x2/config.mk
+++ b/cpu/mcf52x2/config.mk
@@ -26,11 +26,11 @@
 PLATFORM_RELFLAGS += -ffixed-d7 -msep-data
 
 cfg=$(shell grep configs $(OBJTREE)/include/config.h | sed 's/.*<\(configs.*\)>/\1/')
-is5249=$(shell grep CONFIG_M5249 $(TOPDIR)/include/$(cfg))
-is5253=$(shell grep CONFIG_M5253 $(TOPDIR)/include/$(cfg))
-is5271=$(shell grep CONFIG_M5271 $(TOPDIR)/include/$(cfg))
-is5272=$(shell grep CONFIG_M5272 $(TOPDIR)/include/$(cfg))
-is5282=$(shell grep CONFIG_M5282 $(TOPDIR)/include/$(cfg))
+is5249:=$(shell grep CONFIG_M5249 $(TOPDIR)/include/$(cfg))
+is5253:=$(shell grep CONFIG_M5253 $(TOPDIR)/include/$(cfg))
+is5271:=$(shell grep CONFIG_M5271 $(TOPDIR)/include/$(cfg))
+is5272:=$(shell grep CONFIG_M5272 $(TOPDIR)/include/$(cfg))
+is5282:=$(shell grep CONFIG_M5282 $(TOPDIR)/include/$(cfg))
 
 
 ifeq ($(findstring 4.2,$(shell $(CC) --version)),4.2)