diff --git a/RestSharp.Tests/UrlBuilderTests.cs b/RestSharp.Tests/UrlBuilderTests.cs
index a94fef44c..5ea30cd22 100644
--- a/RestSharp.Tests/UrlBuilderTests.cs
+++ b/RestSharp.Tests/UrlBuilderTests.cs
@@ -125,6 +125,17 @@ public void GET_with_resource_containing_tokens()
 			Assert.Equal(expected, output);
 		}
 
+		[Fact]
+		public void GET_with_resource_containing_null_token()
+		{
+			var request = new RestRequest("/resource/{foo}", Method.GET);
+			request.AddUrlSegment("foo", null);
+			var client = new RestClient("http://example.com/api/1.0");
+
+			var exception = Assert.Throws<ArgumentException>(() => client.BuildUri(request));
+			Assert.Contains("foo", exception.Message);
+		}
+
 		[Fact]
 		public void POST_with_resource_containing_tokens()
 		{
diff --git a/RestSharp/RestClient.cs b/RestSharp/RestClient.cs
index 82a990f2b..94f669411 100644
--- a/RestSharp/RestClient.cs
+++ b/RestSharp/RestClient.cs
@@ -248,6 +248,11 @@ public Uri BuildUri(IRestRequest request)
 			var urlParms = request.Parameters.Where(p => p.Type == ParameterType.UrlSegment);
 			foreach (var p in urlParms)
 			{
+				if (p.Value == null)
+				{
+					throw new ArgumentException(string.Format("Cannot build uri when url segment parameter '{0}' value is null.", p.Name), "request");
+				}
+
 				assembled = assembled.Replace("{" + p.Name + "}", p.Value.ToString().UrlEncode());
 			}