diff --git a/ClosedXML/Excel/Cells/XLCell.cs b/ClosedXML/Excel/Cells/XLCell.cs
index da9adbb..2dd6fc7 100644
--- a/ClosedXML/Excel/Cells/XLCell.cs
+++ b/ClosedXML/Excel/Cells/XLCell.cs
@@ -786,12 +786,12 @@
 
             if (!data.Any())
             {
-                if (itemType.IsPrimitive || itemType == typeof(String) || itemType == typeof(DateTime) || itemType.IsNumber())
+                if (itemType.IsSimpleType())
                     maximumColumnNumber = _columnNumber;
                 else
                     maximumColumnNumber = _columnNumber + itemType.GetFields().Length + itemType.GetProperties().Length - 1;
             }
-            else if (itemType.IsPrimitive || itemType == typeof(String) || itemType == typeof(DateTime) || itemType.IsNumber())
+            else if (itemType.IsSimpleType())
             {
                 foreach (object o in data)
                 {
@@ -835,7 +835,7 @@
                 {
                     resetRecordPosition();
 
-                    if (m.GetType().IsPrimitive || m is String || m is DateTime || m is TimeSpan || m.IsNumber())
+                    if (m.GetType().IsSimpleType())
                     {
                         if (addHeadings && !hasHeadings)
                         {
diff --git a/ClosedXML/Extensions.cs b/ClosedXML/Extensions.cs
index 230170d..3ad5be4 100644
--- a/ClosedXML/Extensions.cs
+++ b/ClosedXML/Extensions.cs
@@ -314,6 +314,15 @@
                     || type == typeof(double)
                     || type == typeof(decimal);
         }
+
+        public static bool IsSimpleType(this Type type)
+        {
+            return type.IsPrimitive
+                || type == typeof(String)
+                || type == typeof(DateTime)
+                || type == typeof(TimeSpan)
+                || type.IsNumber();
+        }
     }
 
     internal static class ObjectExtensions