diff --git a/Makefile b/Makefile
index ce36272094..1e7a1277ce 100644
--- a/Makefile
+++ b/Makefile
@@ -1289,10 +1289,6 @@ endif
 ALL_CFLAGS = $(DEVELOPER_CFLAGS) $(CPPFLAGS) $(CFLAGS)
 ALL_LDFLAGS = $(LDFLAGS)
 
-comma := ,
-empty :=
-space := $(empty) $(empty)
-
 ifdef SANITIZE
 SANITIZERS := $(foreach flag,$(subst $(comma),$(space),$(SANITIZE)),$(flag))
 BASIC_CFLAGS += -fsanitize=$(SANITIZE) -fno-sanitize-recover=$(SANITIZE)
diff --git a/shared.mak b/shared.mak
index 1dda948df0..934bf42893 100644
--- a/shared.mak
+++ b/shared.mak
@@ -23,3 +23,11 @@
 #
 #    info make --index-search=.DELETE_ON_ERROR
 .DELETE_ON_ERROR:
+
+### Global variables
+
+## comma, empty, space: handy variables as these tokens are either
+## special or can be hard to spot among other Makefile syntax.
+comma := ,
+empty :=
+space := $(empty) $(empty)