diff --git a/tools/build/Makefile.build b/tools/build/Makefile.build
index 10df57237a66..98cfc388ea33 100644
--- a/tools/build/Makefile.build
+++ b/tools/build/Makefile.build
@@ -94,12 +94,12 @@ obj-y        := $(patsubst %/, %/$(obj)-in.o, $(obj-y))
 subdir-obj-y := $(filter %/$(obj)-in.o, $(obj-y))
 
 # '$(OUTPUT)/dir' prefix to all objects
-prefix       := $(subst ./,,$(OUTPUT)$(dir)/)
-obj-y        := $(addprefix $(prefix),$(obj-y))
-subdir-obj-y := $(addprefix $(prefix),$(subdir-obj-y))
+objprefix    := $(subst ./,,$(OUTPUT)$(dir)/)
+obj-y        := $(addprefix $(objprefix),$(obj-y))
+subdir-obj-y := $(addprefix $(objprefix),$(subdir-obj-y))
 
 # Final '$(obj)-in.o' object
-in-target := $(prefix)$(obj)-in.o
+in-target := $(objprefix)$(obj)-in.o
 
 PHONY += $(subdir-y)