diff --git a/Makefile b/Makefile
index 1a157af..67f2524 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 .PHONY: all prepare force-build build push
 
-IMAGE_NAME:=focs.ji.sjtu.edu.cn:5000/gitea/runner-images:focs-ubuntu-latest-slim
+IMAGE_NAME := focs.ji.sjtu.edu.cn:5000/gitea/runner-images:focs-ubuntu-latest-slim
 
 all: build