diff --git a/Dockerfile b/Dockerfile
index af68e17..4ef2c70 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -10,7 +10,7 @@ RUN apt-get update \
  && apt-get clean \
  && rm -r /var/lib/apt/lists/*
 
-ENV AUTOUPGRADE=1
+ENV AUTO_UPGRADE=1
 ENV LE_WORKING_DIR=/acme.sh
 ENV LE_CONFIG_HOME=/acmecerts
 RUN wget -O- https://get.acme.sh | sh