diff --git a/target/imagebuilder/files/Makefile b/target/imagebuilder/files/Makefile
index aeae98aacd..eadb0ebe85 100644
--- a/target/imagebuilder/files/Makefile
+++ b/target/imagebuilder/files/Makefile
@@ -47,6 +47,7 @@ Building images:
 	make image EXTRA_IMAGE_NAME="<string>" # Add this to the output image filename (sanitized)
 	make image DISABLED_SERVICES="<svc1> [<svc2> [<svc3> ..]]" # Which services in /etc/init.d/ should be disabled
 	make image ADD_LOCAL_KEY=1 # store locally generated signing key in built images
+	make image ROOTFS_PARTSIZE="<size>" # override the default rootfs partition size in MegaBytes
 
 Print manifest:
 	List "all" packages which get installed into the image.
@@ -243,7 +244,8 @@ image:
 		$(if $(FILES),USER_FILES="$(FILES)") \
 		$(if $(PACKAGES),USER_PACKAGES="$(PACKAGES)") \
 		$(if $(BIN_DIR),BIN_DIR="$(BIN_DIR)") \
-		$(if $(DISABLED_SERVICES),DISABLED_SERVICES="$(DISABLED_SERVICES)"))
+		$(if $(DISABLED_SERVICES),DISABLED_SERVICES="$(DISABLED_SERVICES)") \
+		$(if $(ROOTFS_PARTSIZE),CONFIG_TARGET_ROOTFS_PARTSIZE="$(ROOTFS_PARTSIZE)"))
 
 manifest: FORCE
 	$(MAKE) -s _check_profile