diff --git a/globals.mak b/globals.mak
index 9e0b4844c513ae24cbb3feaaf4a96f38e778998b..a467a69a633ae6320259523dc2eaf177b4408fb0 100644
--- a/globals.mak
+++ b/globals.mak
@@ -18,8 +18,8 @@ if BUILD_GSM
 GSMCODEC=-DHAVE_GSM_CODEC
 endif
 
-RING_DIRTY_REPO:=$(shell git diff-index --quiet HEAD 2>/dev/null || echo dirty)
-RING_REVISION:=$(shell git log -1 --format="%h" --abbrev=10 2>/dev/null)
+RING_DIRTY_REPO ?= $(shell git diff-index --quiet HEAD 2>/dev/null || echo dirty)
+RING_REVISION ?= $(shell git log -1 --format="%h" --abbrev=10 2>/dev/null)
 
 # Preprocessor flags
 AM_CPPFLAGS = \