diff --git a/Makefile.include b/Makefile.include
index 1072231bd6..d3b2eb8d7c 100644
--- a/Makefile.include
+++ b/Makefile.include
@@ -350,20 +350,8 @@ include $(RIOTMAKE)/cflags.inc.mk
 # Include VERSION for releases
 -include $(RIOTBASE)/VERSION
 
-# make the RIOT version available to the program
-ifeq ($(origin RIOT_VERSION), undefined)
-  GIT_STRING := $(shell git --git-dir="$(RIOTBASE)/.git" describe --always --abbrev=4 2> /dev/null)
-  ifneq (,$(GIT_STRING))
-    GIT_BRANCH := $(shell git --git-dir="$(RIOTBASE)/.git" rev-parse --abbrev-ref HEAD)
-    ifeq ($(strip $(GIT_BRANCH)),master)
-      RIOT_VERSION := $(GIT_STRING)
-    else
-      RIOT_VERSION := $(GIT_STRING)-$(GIT_BRANCH)
-    endif
-  else
-    RIOT_VERSION := 'UNKNOWN (builddir: $(RIOTBASE))'
-  endif
-endif
+include $(RIOTMAKE)/git_version.inc.mk
+RIOT_VERSION ?= $(or $(GIT_VERSION),'UNKNOWN (builddir: $(RIOTBASE))')
 
 # Set module by prepending APPLICATION name with 'application_'.
 # It prevents conflict with application and modules with the same name.
@@ -733,12 +721,14 @@ $(RIOTBUILD_CONFIG_HEADER_C): FORCE
 	$(Q)'$(RIOTTOOLS)/genconfigheader/genconfigheader.sh' $(CFLAGS_WITH_MACROS) \
 		| '$(LAZYSPONGE)' $(LAZYSPONGE_FLAGS) '$@'
 
-CFLAGS_WITH_MACROS := $(CFLAGS)
+# Immediate evaluation but keep CLAGS_WITH_MACROS deferred
+_CFLAGS := $(CFLAGS)
+CFLAGS_WITH_MACROS = $(_CFLAGS)
 
 ifneq (,$(RIOT_VERSION_OVERRIDE))
-export CFLAGS_WITH_MACROS += -DRIOT_VERSION=\"$(RIOT_VERSION_OVERRIDE)\"
+  CFLAGS_WITH_MACROS += -DRIOT_VERSION=\"$(RIOT_VERSION_OVERRIDE)\"
 else
-export CFLAGS_WITH_MACROS += -DRIOT_VERSION=\"$(RIOT_VERSION)\"
+  CFLAGS_WITH_MACROS += -DRIOT_VERSION=\"$(RIOT_VERSION)\"
 endif
 
 CFLAGS := $(patsubst -D%,,$(CFLAGS))
diff --git a/makefiles/git_version.inc.mk b/makefiles/git_version.inc.mk
new file mode 100644
index 0000000000..03a2194564
--- /dev/null
+++ b/makefiles/git_version.inc.mk
@@ -0,0 +1,11 @@
+# GIT_VERSION is git description + branch name if it not master
+# Empty when not in a git repository
+#
+#   2019.10-devel-97-g3bcc72
+#   2019.10-devel-97-g3bcc72-pr/git_version
+
+GIT_DESCRIBE = $(call memoized,GIT_DESCRIBE,$(shell git --git-dir="$(RIOTBASE)/.git" describe --always --abbrev=4 2> /dev/null))
+GIT_BRANCH = $(call memoized,GIT_BRANCH,$(shell git --git-dir="$(RIOTBASE)/.git" rev-parse --abbrev-ref HEAD))
+_GIT_VERSION = $(GIT_DESCRIBE)$(addprefix -,$(GIT_BRANCH:master=))
+
+GIT_VERSION ?= $(if $(GIT_DESCRIBE),$(_GIT_VERSION))