diff --git a/bin/emqx b/bin/emqx
index c26c0f8fc..3d5900ef7 100755
--- a/bin/emqx
+++ b/bin/emqx
@@ -20,8 +20,8 @@ mkdir -p "$RUNNER_LOG_DIR"
 # Make sure data directory exists
 mkdir -p "$RUNNER_DATA_DIR"
 
-# cuttlefish try to read environment variables starting with "EMQX_", if not specified
-export CUTTLEFISH_ENV_OVERRIDE_PREFIX="${CUTTLEFISH_ENV_OVERRIDE_PREFIX:-EMQX_}"
+# cuttlefish try to read environment variables starting with "EMQX_"
+export CUTTLEFISH_ENV_OVERRIDE_PREFIX='EMQX_'
 
 relx_usage() {
     command="$1"