diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/launch/DefaultLauncher.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/launch/DefaultLauncher.java
index 777be6b75e..b299086799 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/launch/DefaultLauncher.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/launch/DefaultLauncher.java
@@ -172,7 +172,7 @@ private Command generateCommandLine(Path nativeFolder) throws IOException {
 
             Proxy.Type proxyType = options.getProxyType();
             if (proxyType == null) {
-                res.addDefault("-Djava.net.useSystemProxies", "true");
+                res.addDefault("-Djava.net.useSystemProxies=", "true");
             } else {
                 String proxyHost = options.getProxyHost();
                 int proxyPort = options.getProxyPort();