diff --git a/Src/Newtonsoft.Json.Tests/Issues/Issue1593.cs b/Src/Newtonsoft.Json.Tests/Issues/Issue1593.cs
new file mode 100644
index 00000000..3164e6ee
--- /dev/null
+++ b/Src/Newtonsoft.Json.Tests/Issues/Issue1593.cs
@@ -0,0 +1,81 @@
+#region License
+// Copyright (c) 2007 James Newton-King
+//
+// Permission is hereby granted, free of charge, to any person
+// obtaining a copy of this software and associated documentation
+// files (the "Software"), to deal in the Software without
+// restriction, including without limitation the rights to use,
+// copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following
+// conditions:
+//
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+// OTHER DEALINGS IN THE SOFTWARE.
+#endregion
+
+#if !(NET20 || NET35)
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Dynamic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using Newtonsoft.Json.Linq;
+using Newtonsoft.Json.Serialization;
+#if DNXCORE50
+using Xunit;
+using Test = Xunit.FactAttribute;
+using Assert = Newtonsoft.Json.Tests.XUnitAssert;
+#else
+using NUnit.Framework;
+#endif
+
+namespace Newtonsoft.Json.Tests.Issues
+{
+    [TestFixture]
+    public class Issue1593 : TestFixtureBase
+    {
+        [Test]
+        public void Test()
+        {
+            string json = JsonConvert.SerializeObject(CreateModel());
+            Assert.AreEqual(@"{""Specific"":2,""A"":1}", json);
+        }
+
+        class BaseModel
+        {
+            public BaseModel()
+            {
+                Extra = new ExpandoObject();
+            }
+            [JsonExtensionData]
+            public ExpandoObject Extra { get; set; }
+        }
+
+        class SpecificModel : BaseModel
+        {
+            public int Specific { get; set; }
+        }
+
+        BaseModel CreateModel()
+        {
+            var model = new SpecificModel();
+            var extra = model.Extra as IDictionary<string, object>;
+            extra["A"] = 1;
+            model.Specific = 2;
+            return model;
+        }
+    }
+}
+#endif
\ No newline at end of file
diff --git a/Src/Newtonsoft.Json/Serialization/DefaultContractResolver.cs b/Src/Newtonsoft.Json/Serialization/DefaultContractResolver.cs
index eebca012..849ec75f 100644
--- a/Src/Newtonsoft.Json/Serialization/DefaultContractResolver.cs
+++ b/Src/Newtonsoft.Json/Serialization/DefaultContractResolver.cs
@@ -495,6 +495,13 @@ namespace Newtonsoft.Json.Serialization
                  : null;
                 Func<object> createExtensionDataDictionary = JsonTypeReflector.ReflectionDelegateFactory.CreateDefaultConstructor<object>(createdType);
                 MethodInfo addMethod = t.GetMethod("Add", new[] { keyType, valueType });
+                if (addMethod == null)
+                {
+                    // Add is explicitly implemented and non-public
+                    // get from dictionary interface
+                    addMethod = dictionaryType.GetMethod("Add", new[] {keyType, valueType});
+                }
+
                 MethodCall<object, object> setExtensionDataDictionaryValue = JsonTypeReflector.ReflectionDelegateFactory.CreateMethodCall<object>(addMethod);
 
                 ExtensionDataSetter extensionDataSetter = (o, key, value) =>