diff --git a/common_arm/Makefile.hal b/common_arm/Makefile.hal
index 2ab6e1ddf..40e0a2c51 100644
--- a/common_arm/Makefile.hal
+++ b/common_arm/Makefile.hal
@@ -139,7 +139,9 @@ endif
 ifneq ($(strip $(filter $(PLATFORM_DEFS),$(STANDALONE_REQ_DEFS))),$(strip $(STANDALONE_REQ_DEFS)))
     $(error Chosen Standalone mode $(STANDALONE) requires $(strip $(STANDALONE_REQ_DEFS)), unsupported by $(PLTNAME))
 endif
-PLATFORM_DEFS+=$(STANDALONE_PLATFORM_DEFS)
+ifneq (,$(STANDALONE_PLATFORM_DEFS))
+    PLATFORM_DEFS+=$(STANDALONE_PLATFORM_DEFS)
+endif
 
 $(info $(findstring WITH_STANDALONE_*,$(PLATFORM_DEFS)))