diff --git a/src/NetCoreForce.Client/ForceClient.cs b/src/NetCoreForce.Client/ForceClient.cs
index f8bea80..5764891 100644
--- a/src/NetCoreForce.Client/ForceClient.cs
+++ b/src/NetCoreForce.Client/ForceClient.cs
@@ -597,14 +597,15 @@ public async Task<SObjectBasicInfo> GetObjectBasicInfo(string objectTypeName)
         /// <para>Use the SObject Describe resource to retrieve all the metadata for an object, including information about each field, URLs, and child relationships.</para>
         /// </summary>
         /// <param name="objectTypeName">SObject name, e.g. Account</param>
+        /// <param name="customHeaders">Example If-Modified-Since: Wed, 3 Jul 2013 19:43:31 GMT</param>
         /// <returns>Returns SObjectMetadataAll with full object meta including field metadata</returns>
-        public async Task<SObjectDescribeFull> GetObjectDescribe(string objectTypeName)
+        public async Task<SObjectDescribeFull> GetObjectDescribe(string objectTypeName, Dictionary<string, string> customHeaders = null)
         {
             var uri = UriFormatter.SObjectDescribe(InstanceUrl, ApiVersion, objectTypeName);
 
             JsonClient client = new JsonClient(AccessToken, _httpClient);
 
-            return await client.HttpGetAsync<SObjectDescribeFull>(uri);
+            return await client.HttpGetAsync<SObjectDescribeFull>(uri, customHeaders);
         }
 
         /// <summary>
diff --git a/src/NetCoreForce.Client/JsonClient.cs b/src/NetCoreForce.Client/JsonClient.cs
index 7721b0f..e647ead 100644
--- a/src/NetCoreForce.Client/JsonClient.cs
+++ b/src/NetCoreForce.Client/JsonClient.cs
@@ -192,6 +192,15 @@ private async Task<T> GetResponse<T>(HttpRequestMessage request, Dictionary<stri
                 return JsonConvert.DeserializeObject<T>(string.Empty);
             }
 
+            // returned when header If-Modified-Since used and the object requested wasn't modified since provided date
+            if (responseMessage.StatusCode == HttpStatusCode.NotModified)
+            {
+                if (customHeaders != null && customHeaders.ContainsKey("If-Modified-Since"))
+                {
+                    return JsonConvert.DeserializeObject<T>(string.Empty);
+                }
+            }
+
             //sucessful response, skip deserialization of response content
             if (responseMessage.IsSuccessStatusCode && !deserializeResponse)
             {