diff --git a/Makefile b/Makefile
index a76bc80f..cb630afb 100755
--- a/Makefile
+++ b/Makefile
@@ -60,7 +60,7 @@ 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))
 
@@ -623,4 +623,4 @@ split-test-packages:$(BUILDDIR)/packages.txt
 	$(SPLIT_CMD) -d -n l/$(NUM_SPLIT) $< $<.
 
 test-group-%:split-test-packages
-	cat $(BUILDDIR)/packages.txt.$* | xargs go test -mod=readonly -timeout=10m -race -coverprofile=$(BUILDDIR)/$*.profile.out
\ No newline at end of file
+	cat $(BUILDDIR)/packages.txt.$* | xargs go test -mod=readonly -timeout=10m -race -coverprofile=$(BUILDDIR)/$*.profile.out