diff --git a/miniupnpd/gitrev.mk b/miniupnpd/gitrev.mk
index cb59fce..a1f48b9 100644
--- a/miniupnpd/gitrev.mk
+++ b/miniupnpd/gitrev.mk
@@ -1,9 +1,9 @@
-# (c) 2019 Thomas Bernard
+# (c) 2019-2020 Thomas Bernard
 # For GNU Make
 
 ISGITREPO := $(shell git rev-parse --is-inside-work-tree)
 ifeq ($(ISGITREPO),true)
 GITREF := $(shell git rev-parse --short HEAD)
 GITBRANCH := $(shell git rev-parse --abbrev-ref HEAD)
-CFLAGS += -DMINIUPNPD_GIT_REF=\"$(GITBRANCH)-$(GITREF)\"
+CPPFLAGS += -DMINIUPNPD_GIT_REF=\"$(GITBRANCH)-$(GITREF)\"
 endif