diff --git a/cpu/atmega_common/Makefile.include b/cpu/atmega_common/Makefile.include
index f6a58df971d39b773b180aa6f2a276f538513369..b7edf393986086a0cdd315858e6ad98b2928d982 100644
--- a/cpu/atmega_common/Makefile.include
+++ b/cpu/atmega_common/Makefile.include
@@ -28,9 +28,10 @@ ifeq ($(LTO),1)
 endif
 
 # Use ROM_LEN and RAM_LEN during link
-# It is made optional until all boards are updated
-LINKFLAGS += $(if $(ROM_LEN),$(LINKFLAGPREFIX)--defsym=__TEXT_REGION_LENGTH__=$(ROM_LEN))
-LINKFLAGS += $(if $(RAM_LEN),$(LINKFLAGPREFIX)--defsym=__DATA_REGION_LENGTH__=$(RAM_LEN))
+$(if $(ROM_LEN),,$(error ROM_LEN is not defined))
+$(if $(RAM_LEN),,$(error RAM_LEN is not defined))
+LINKFLAGS += $(LINKFLAGPREFIX)--defsym=__TEXT_REGION_LENGTH__=$(ROM_LEN)
+LINKFLAGS += $(LINKFLAGPREFIX)--defsym=__DATA_REGION_LENGTH__=$(RAM_LEN)
 
 # Use newer linker script to have ROM/RAM configuration symbols in binutils<2.26
 LDSCRIPT_COMPAT = $(if $(shell $(TARGET_ARCH)-ld --verbose | grep __TEXT_REGION_LENGTH__),,\