diff --git a/device.mk b/device.mk
index 2a870ce..9e4b875 100644
--- a/device.mk
+++ b/device.mk
@@ -41,6 +41,17 @@
 
 TARGET_SYSTEM_PROP := device/$(TARGET_VENDOR)/$(PRODUCT_NAME)/system.prop
 
+# Define the build number based on the product flavour and on the build manifest
+# revision
+ifneq (,$(strip $(PRODUCT_FLAVOR)))
+  _BUILD_MANIFEST_REV := $(shell (git -C $(TOPDIR).repo/manifests rev-parse --short=8 HEAD))
+  BUILD_NUMBER := $(PRODUCT_FLAVOR)-$(_BUILD_MANIFEST_REV)
+  HAS_BUILD_NUMBER := true
+else
+  $(error PRODUCT_FLAVOR must be defined)
+endif
+$(warning Build defined as $(BUILD_ID) ($(BUILD_NUMBER)))
+
 
 # We don't have the calibration data as this sort of
 # data can only be generated at the factory so don't generate persist.img