diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs
index 54d233e..b313949 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs
@@ -1201,7 +1201,7 @@
                     autoFilter.Filters.Add((int)filterColumn.ColumnId.Value + 1, filterList);
 
                     Boolean isText = false;
-                    foreach (Filter filter in filterColumn.Filters)
+                    foreach (Filter filter in filterColumn.Filters.OfType<Filter>())
                     {
                         Double dTest;
                         String val = filter.Val.Value;
@@ -1212,7 +1212,7 @@
                         }
                     }
 
-                    foreach (Filter filter in filterColumn.Filters)
+                    foreach (Filter filter in filterColumn.Filters.OfType<Filter>())
                     {
                         var xlFilter = new XLFilter { Connector = XLConnector.Or, Operator = XLFilterOperator.Equal };
 
diff --git a/ClosedXML/ClosedXML/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj b/ClosedXML/ClosedXML/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj
index 270798f..3428368 100644
--- a/ClosedXML/ClosedXML/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj
+++ b/ClosedXML/ClosedXML/ClosedXML_Sandbox/ClosedXML_Sandbox.csproj
@@ -126,7 +126,7 @@
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\ClosedXML\ClosedXML.csproj">
-      <Project>{BD5E6BFE-E837-4A35-BCA9-39667D873A20}</Project>
+      <Project>{bd5e6bfe-e837-4a35-bca9-39667d873a20}</Project>
       <Name>ClosedXML</Name>
     </ProjectReference>
     <ProjectReference Include="..\ClosedXML_Examples\ClosedXML_Examples.csproj">
diff --git a/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs b/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs
index 5145c4d..82da5f5 100644
--- a/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs
+++ b/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs
@@ -15,29 +15,19 @@
 
         static void Main(string[] args)
         {
-            var wb = new XLWorkbook();
-
-            Console.WriteLine("Creating");
-            var start = DateTime.Now;
-            foreach (var sheetId in Enumerable.Range(1, 4))
-            {
-                var ws = wb.AddWorksheet("Sheet" + sheetId);
-                foreach (var ro in Enumerable.Range(1, 4000))
-                {
-                    foreach (var co in Enumerable.Range(1, 30))
-                    {
-                        ws.Cell(ro, co).Value = String.Format("({0}, {1})", ro, co);
-                    }
-                }
-            }
-            var end = DateTime.Now;
-            Console.WriteLine((end - start).TotalSeconds);
-
+            DateTime start, end;
+            var values = new List<Double>();
+            var wb = new XLWorkbook(@"c:\temp\issue.xlsx");
+            
             Console.WriteLine("Saving");
             start = DateTime.Now;
             wb.SaveAs(@"c:\temp\saved.xlsx");
             end = DateTime.Now;
-            Console.WriteLine((end - start).TotalSeconds);
+            values.Add((end - start).TotalMinutes);
+
+            Console.WriteLine("Average: " + values.Average());
+            Console.WriteLine("Min: " + values.Min());
+            Console.WriteLine("Max: " + values.Max());
 
             Console.WriteLine("Done");
             Console.ReadKey();