diff --git a/core/java/android/net/http/X509TrustManagerExtensions.java b/core/java/android/net/http/X509TrustManagerExtensions.java
index eb4cedab83b79c5cec1d457b31da3b25c0f7a3a6..7c23c2319f4d5edbae17ad2fb5619ba38d3ce3c9 100644
--- a/core/java/android/net/http/X509TrustManagerExtensions.java
+++ b/core/java/android/net/http/X509TrustManagerExtensions.java
@@ -18,6 +18,9 @@ package android.net.http;
 
 import com.android.org.conscrypt.TrustManagerImpl;
 
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.security.cert.CertificateException;
 import java.security.cert.X509Certificate;
 import java.util.List;
@@ -34,7 +37,11 @@ import javax.net.ssl.X509TrustManager;
  */
 public class X509TrustManagerExtensions {
 
-    final TrustManagerImpl mDelegate;
+    private final TrustManagerImpl mDelegate;
+    // Methods to use when mDelegate is not a TrustManagerImpl and duck typing is being used.
+    private final X509TrustManager mTrustManager;
+    private final Method mCheckServerTrusted;
+    private final Method mIsUserAddedCertificate;
 
     /**
      * Constructs a new X509TrustManagerExtensions wrapper.
@@ -45,10 +52,31 @@ public class X509TrustManagerExtensions {
     public X509TrustManagerExtensions(X509TrustManager tm) throws IllegalArgumentException {
         if (tm instanceof TrustManagerImpl) {
             mDelegate = (TrustManagerImpl) tm;
-        } else {
-            mDelegate = null;
-            throw new IllegalArgumentException("tm is an instance of " + tm.getClass().getName() +
-                    " which is not a supported type of X509TrustManager");
+            mTrustManager = null;
+            mCheckServerTrusted = null;
+            mIsUserAddedCertificate = null;
+            return;
+        }
+        // Use duck typing if possible.
+        mDelegate = null;
+        mTrustManager = tm;
+        // Check that the hostname aware checkServerTrusted is present.
+        try {
+            mCheckServerTrusted = tm.getClass().getMethod("checkServerTrusted",
+                    X509Certificate[].class,
+                    String.class,
+                    String.class);
+        } catch (NoSuchMethodException e) {
+            throw new IllegalArgumentException("Required method"
+                    + " checkServerTrusted(X509Certificate[], String, String, String) missing");
+        }
+        // Check that isUserAddedCertificate is present.
+        try {
+            mIsUserAddedCertificate = tm.getClass().getMethod("isUserAddedCertificate",
+                    X509Certificate.class);
+        } catch (NoSuchMethodException e) {
+            throw new IllegalArgumentException(
+                    "Required method isUserAddedCertificate(X509Certificate) missing");
         }
     }
 
@@ -64,7 +92,24 @@ public class X509TrustManagerExtensions {
      */
     public List<X509Certificate> checkServerTrusted(X509Certificate[] chain, String authType,
                                                     String host) throws CertificateException {
-        return mDelegate.checkServerTrusted(chain, authType, host);
+        if (mDelegate != null) {
+            return mDelegate.checkServerTrusted(chain, authType, host);
+        } else {
+            try {
+                return (List<X509Certificate>) mCheckServerTrusted.invoke(mTrustManager, chain,
+                        authType, host);
+            } catch (IllegalAccessException e) {
+                throw new CertificateException("Failed to call checkServerTrusted", e);
+            } catch (InvocationTargetException e) {
+                if (e.getCause() instanceof CertificateException) {
+                    throw (CertificateException) e.getCause();
+                }
+                if (e.getCause() instanceof RuntimeException) {
+                    throw (RuntimeException) e.getCause();
+                }
+                throw new CertificateException("checkServerTrusted failed", e.getCause());
+            }
+        }
     }
 
     /**
@@ -78,6 +123,20 @@ public class X509TrustManagerExtensions {
      * otherwise.
      */
     public boolean isUserAddedCertificate(X509Certificate cert) {
-        return mDelegate.isUserAddedCertificate(cert);
+        if (mDelegate != null) {
+            return mDelegate.isUserAddedCertificate(cert);
+        } else {
+            try {
+                return (Boolean) mIsUserAddedCertificate.invoke(mTrustManager, cert);
+            } catch (IllegalAccessException e) {
+                throw new RuntimeException("Failed to call isUserAddedCertificate", e);
+            } catch (InvocationTargetException e) {
+                if (e.getCause() instanceof RuntimeException) {
+                    throw (RuntimeException) e.getCause();
+                } else {
+                    throw new RuntimeException("isUserAddedCertificate failed", e.getCause());
+                }
+            }
+        }
     }
 }