diff --git a/docker/nginx/nginx.conf b/docker/nginx/nginx.conf
index a6883cb8..c8da6b0f 100644
--- a/docker/nginx/nginx.conf
+++ b/docker/nginx/nginx.conf
@@ -70,7 +70,7 @@ http {
     proxy_http_version 1.1;
 
     # proxy cache definition
-    proxy_cache_path /data/nginx/cache levels=1:2 keys_zone=skynet:10m max_size=50g inactive=48h use_temp_path=off;
+    proxy_cache_path /data/nginx/cache levels=1:2 keys_zone=skynet:10m max_size=50g min_free=100g inactive=48h use_temp_path=off;
 
     # this runs before forking out nginx worker processes
     init_by_lua_block {