diff --git a/Dockerfile b/Dockerfile
index f7f2d6f64..52cb18c6b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -17,5 +17,5 @@ RUN npm link @koush/opencv4nodejs
 
 RUN npm run build
 
-ENV COMMIT_SHA=$GITHUB_SHA
+ENV COMMIT_SHA=${GITHUB_SHA}
 CMD npm run serve-no-build