diff --git a/module/Makefile b/module/Makefile
index 04dc9f50a..42503ad41 100644
--- a/module/Makefile
+++ b/module/Makefile
@@ -39,7 +39,7 @@ build_tags += $(BUILD_TAGS)
 build_tags := $(strip $(build_tags))
 
 whitespace :=
-whitespace += $(whitespace)
+whitespace := $(whitespace) $(whitespace)
 comma := ,
 build_tags_comma_sep := $(subst $(whitespace),$(comma),$(build_tags))