diff --git a/Dockerfile b/Dockerfile
index e41b3aa..dfccecc 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -7,7 +7,7 @@ FROM python:${PYTHON_VERSION}-alpine${ALPINE_VERSION}
 
 RUN apk update && apk add less
 
-RUN pip install rotate-backups==${ROTATE_BACKUPS_VERSION}
+RUN pip install rotate-backups==$ROTATE_BACKUPS_VERSION
 
 RUN mkdir /data