diff --git a/Makefile.inc b/Makefile.inc
index 648bc4f7f2..1f18726e5d 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -159,7 +159,7 @@ ws_to_under=$(shell echo '$1' | tr ' \t' '_')
 #######################################################################
 # Helper functions for ramstage postprocess
 spc :=
-spc +=
+spc := $(spc) $(spc)
 comma := ,
 
 # Returns all files and dirs below `dir` (recursively).