diff --git a/library/src/org/whispersystems/textsecure/push/PushServiceSocket.java b/library/src/org/whispersystems/textsecure/push/PushServiceSocket.java
index abae23f565..f9c88e7630 100644
--- a/library/src/org/whispersystems/textsecure/push/PushServiceSocket.java
+++ b/library/src/org/whispersystems/textsecure/push/PushServiceSocket.java
@@ -1,3 +1,19 @@
+/**
+ * Copyright (C) 2014 Open Whisper Systems
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.whispersystems.textsecure.push;
 
 import android.content.Context;
@@ -10,6 +26,7 @@ import org.apache.http.conn.ssl.StrictHostnameVerifier;
 import org.whispersystems.textsecure.crypto.IdentityKey;
 import org.whispersystems.textsecure.storage.PreKeyRecord;
 import org.whispersystems.textsecure.util.Base64;
+import org.whispersystems.textsecure.util.BlacklistingTrustManager;
 import org.whispersystems.textsecure.util.Util;
 
 import java.io.File;
@@ -32,8 +49,15 @@ import java.util.Set;
 
 import javax.net.ssl.HttpsURLConnection;
 import javax.net.ssl.SSLContext;
+import javax.net.ssl.TrustManager;
 import javax.net.ssl.TrustManagerFactory;
 
+/**
+ *
+ * Network interface to the TextSecure server API.
+ *
+ * @author Moxie Marlinspike
+ */
 public class PushServiceSocket {
 
   private static final String CREATE_ACCOUNT_SMS_PATH   = "/v1/accounts/sms/code/%s";
@@ -51,20 +75,20 @@ public class PushServiceSocket {
 
   private static final boolean ENFORCE_SSL = true;
 
-  private final Context context;
-  private final String serviceUrl;
-  private final String localNumber;
-  private final String password;
-  private final TrustManagerFactory trustManagerFactory;
+  private final Context        context;
+  private final String         serviceUrl;
+  private final String         localNumber;
+  private final String         password;
+  private final TrustManager[] trustManagers;
 
   public PushServiceSocket(Context context, String serviceUrl, TrustStore trustStore,
                            String localNumber, String password)
   {
-    this.context             = context.getApplicationContext();
-    this.serviceUrl          = serviceUrl;
-    this.localNumber         = localNumber;
-    this.password            = password;
-    this.trustManagerFactory = initializeTrustManagerFactory(trustStore);
+    this.context       = context.getApplicationContext();
+    this.serviceUrl    = serviceUrl;
+    this.localNumber   = localNumber;
+    this.password      = password;
+    this.trustManagers = initializeTrustManager(trustStore);
   }
 
   public void createAccount(boolean voice) throws IOException {
@@ -356,7 +380,7 @@ public class PushServiceSocket {
   private HttpURLConnection getConnection(String urlFragment, String method) throws IOException {
     try {
       SSLContext context = SSLContext.getInstance("TLS");
-      context.init(null, trustManagerFactory.getTrustManagers(), null);
+      context.init(null, trustManagers, null);
 
       URL url = new URL(String.format("%s%s", serviceUrl, urlFragment));
       Log.w("PushServiceSocket", "Push service URL: " + serviceUrl);
@@ -394,7 +418,7 @@ public class PushServiceSocket {
     }
   }
 
-  private TrustManagerFactory initializeTrustManagerFactory(TrustStore trustStore) {
+  private TrustManager[] initializeTrustManager(TrustStore trustStore) {
     try {
       InputStream keyStoreInputStream = trustStore.getKeyStoreInputStream();
       KeyStore    keyStore            = KeyStore.getInstance("BKS");
@@ -404,7 +428,7 @@ public class PushServiceSocket {
       TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance("X509");
       trustManagerFactory.init(keyStore);
 
-      return trustManagerFactory;
+      return BlacklistingTrustManager.createFor(trustManagerFactory.getTrustManagers());
     } catch (KeyStoreException kse) {
       throw new AssertionError(kse);
     } catch (CertificateException e) {
diff --git a/library/src/org/whispersystems/textsecure/util/BlacklistingTrustManager.java b/library/src/org/whispersystems/textsecure/util/BlacklistingTrustManager.java
new file mode 100644
index 0000000000..e6c6c4b069
--- /dev/null
+++ b/library/src/org/whispersystems/textsecure/util/BlacklistingTrustManager.java
@@ -0,0 +1,87 @@
+/**
+ * Copyright (C) 2014 Open Whisper Systems
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.whispersystems.textsecure.util;
+
+import java.math.BigInteger;
+import java.security.cert.CertificateException;
+import java.security.cert.X509Certificate;
+import java.util.LinkedList;
+import java.util.List;
+
+import javax.net.ssl.TrustManager;
+import javax.net.ssl.X509TrustManager;
+
+/**
+ * Trust manager that defers to a system X509 trust manager, and
+ * additionally rejects certificates if they have a blacklisted
+ * serial.
+ *
+ * @author Moxie Marlinspike
+ */
+public class BlacklistingTrustManager implements X509TrustManager {
+
+  private static final List<BigInteger> BLACKLIST = new LinkedList<BigInteger>() {{
+    add(new BigInteger("4098"));
+  }};
+
+  public static TrustManager[] createFor(TrustManager[] trustManagers) {
+    for (TrustManager trustManager : trustManagers) {
+      if (trustManager instanceof X509TrustManager) {
+        TrustManager[] results = new BlacklistingTrustManager[1];
+        results[0] = new BlacklistingTrustManager((X509TrustManager)trustManager);
+
+        return results;
+      }
+    }
+
+    throw new AssertionError("No X509 Trust Managers!");
+  }
+
+  private final X509TrustManager trustManager;
+
+  public BlacklistingTrustManager(X509TrustManager trustManager) {
+    this.trustManager = trustManager;
+  }
+
+  @Override
+  public void checkClientTrusted(X509Certificate[] chain, String authType)
+      throws CertificateException
+  {
+    trustManager.checkClientTrusted(chain, authType);
+  }
+
+  @Override
+  public void checkServerTrusted(X509Certificate[] chain, String authType)
+      throws CertificateException
+  {
+    trustManager.checkServerTrusted(chain, authType);
+
+    for (X509Certificate certificate : chain) {
+      for (BigInteger blacklistedSerial : BLACKLIST) {
+        if (certificate.getSerialNumber().equals(blacklistedSerial)) {
+          throw new CertificateException("Blacklisted Serial: " + certificate.getSerialNumber());
+        }
+      }
+    }
+
+  }
+
+  @Override
+  public X509Certificate[] getAcceptedIssuers() {
+    return trustManager.getAcceptedIssuers();
+  }
+}