diff --git a/rustup.sh b/rustup.sh
index 6f7b29e..d4b1a3e 100755
--- a/rustup.sh
+++ b/rustup.sh
@@ -5,7 +5,8 @@ cd "$TUNASYNC_WORKING_DIR"
 echo "rustup sync started"
 
 BASE_URL=${MIRROR_BASE_URL:-"https://mirrors.tuna.tsinghua.edu.cn/rustup"}
+GC=${RUSTUP_GC:-"30"}
 
-/usr/local/cargo/bin/rustup-mirror -u "${BASE_URL}" -m "${TUNASYNC_WORKING_DIR}" --gc 30
+/usr/local/cargo/bin/rustup-mirror -u "${BASE_URL}" -m "${TUNASYNC_WORKING_DIR}" --gc "${GC}"
 echo "finished"