diff --git a/Makefile.dep b/Makefile.dep
index 900e87685e..0de7d7ec19 100644
--- a/Makefile.dep
+++ b/Makefile.dep
@@ -5,6 +5,13 @@ OLD_USEPKG := $(sort $(USEPKG))
 # include board dependencies
 -include $(RIOTBOARD)/$(BOARD)/Makefile.dep
 
+# Transitional conditional include until all boards define 'CPU' in
+# Makefile.features
+ifneq (,$(CPU))
+  # include cpu dependencies
+  -include $(RIOTCPU)/$(CPU)/Makefile.dep
+endif
+
 # include external modules dependencies
 # processed before RIOT ones to be evaluated before the 'default' rules.
 -include $(EXTERNAL_MODULE_DIRS:%=%/Makefile.dep)