diff --git a/src/PortableRest.Tests/ResourceUriTests.cs b/src/PortableRest.Tests/ResourceUriTests.cs
index 1ff7202..91af8c2 100644
--- a/src/PortableRest.Tests/ResourceUriTests.cs
+++ b/src/PortableRest.Tests/ResourceUriTests.cs
@@ -87,5 +87,15 @@ public void BuildResourceUriWhereResourceUriIsNull()
             Assert.AreEqual("https://www.googleapis.com/discovery/v1/apis?&name=adexchangebuyer", 
                 request.GetResourceUri("https://www.googleapis.com/discovery/v1/apis?&name=adexchangebuyer").ToString());
         }
+
+        [TestMethod]
+        public void TestUriIdempodence()
+        {
+            var request = new RestRequest("/test");
+            request.AddQueryString("test", "value");
+            var originalResource = request.Resource;
+            request.GetResourceUri("http://some.base.url");
+            Assert.AreEqual(originalResource, request.Resource);
+        }
     }
 }
\ No newline at end of file
diff --git a/src/PortableRest/RestRequest.cs b/src/PortableRest/RestRequest.cs
index 3dcbfbb..6ec6854 100644
--- a/src/PortableRest/RestRequest.cs
+++ b/src/PortableRest/RestRequest.cs
@@ -252,9 +252,10 @@ public void AddQueryString(string key, object value)
         /// <returns></returns>
         public Uri GetResourceUri(string baseUrl)
         {
+            string resource = Resource; 
             foreach (var segment in UrlSegments.Where(c => !c.IsQueryString))
             {
-                Resource = Resource.Replace("{" + segment.Key + "}", Uri.EscapeUriString(segment.Value));
+                resource = resource.Replace("{" + segment.Key + "}", Uri.EscapeUriString(segment.Value));
             }
 
             if (UrlSegments.Any(c => c.IsQueryString))
@@ -265,12 +266,12 @@ public Uri GetResourceUri(string baseUrl)
                             current.Append(string.Format("&{0}={1}", Uri.EscapeUriString(next.Key), Uri.EscapeDataString(next.Value))))
                     .ToString();
 
-                Resource = string.Format(Resource.Contains("?") ? "{0}{1}" : "{0}?{1}", Resource, queryString);
+                resource = string.Format(resource.Contains("?") ? "{0}{1}" : "{0}?{1}", resource, queryString);
             }
 
-            Resource = CombineUriParts(baseUrl, Resource);
+            resource = CombineUriParts(baseUrl, resource);
 
-            return new Uri(Resource, UriKind.RelativeOrAbsolute);
+            return new Uri(resource, UriKind.RelativeOrAbsolute);
         }
 
         #endregion