diff --git a/core/java/android/net/ProxyProperties.java b/core/java/android/net/ProxyProperties.java
index 78ac75f..010e527 100644
--- a/core/java/android/net/ProxyProperties.java
+++ b/core/java/android/net/ProxyProperties.java
@@ -139,6 +139,17 @@
         return false;
     }
 
+    public boolean isValid() {
+        if (!TextUtils.isEmpty(mPacFileUrl)) return true;
+        try {
+            Proxy.validate(mHost == null ? "" : mHost, mPort == 0 ? "" : Integer.toString(mPort),
+                    mExclusionList == null ? "" : mExclusionList);
+        } catch (IllegalArgumentException e) {
+            return false;
+        }
+        return true;
+    }
+
     public java.net.Proxy makeProxy() {
         java.net.Proxy proxy = java.net.Proxy.NO_PROXY;
         if (mHost != null) {
diff --git a/services/java/com/android/server/ConnectivityService.java b/services/java/com/android/server/ConnectivityService.java
index 7910147..52c7b40 100644
--- a/services/java/com/android/server/ConnectivityService.java
+++ b/services/java/com/android/server/ConnectivityService.java
@@ -3351,6 +3351,11 @@
             String pacFileUrl = "";
             if (proxyProperties != null && (!TextUtils.isEmpty(proxyProperties.getHost()) ||
                     !TextUtils.isEmpty(proxyProperties.getPacFileUrl()))) {
+                if (!proxyProperties.isValid()) {
+                    if (DBG)
+                        log("Invalid proxy properties, ignoring: " + proxyProperties.toString());
+                    return;
+                }
                 mGlobalProxy = new ProxyProperties(proxyProperties);
                 host = mGlobalProxy.getHost();
                 port = mGlobalProxy.getPort();
@@ -3394,6 +3399,11 @@
             } else {
                 proxyProperties = new ProxyProperties(host, port, exclList);
             }
+            if (!proxyProperties.isValid()) {
+                if (DBG) log("Invalid proxy properties, ignoring: " + proxyProperties.toString());
+                return;
+            }
+
             synchronized (mProxyLock) {
                 mGlobalProxy = proxyProperties;
             }
@@ -3418,6 +3428,10 @@
         synchronized (mProxyLock) {
             if (mDefaultProxy != null && mDefaultProxy.equals(proxy)) return;
             if (mDefaultProxy == proxy) return; // catches repeated nulls
+            if (!proxy.isValid()) {
+                if (DBG) log("Invalid proxy properties, ignoring: " + proxy.toString());
+                return;
+            }
             mDefaultProxy = proxy;
 
             if (mGlobalProxy != null) return;