diff --git a/ClosedXML/ClosedXML/ClosedXML/XLHelper.cs b/ClosedXML/ClosedXML/ClosedXML/XLHelper.cs
index 150a059..8f5f073 100644
--- a/ClosedXML/ClosedXML/ClosedXML/XLHelper.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/XLHelper.cs
@@ -62,7 +62,15 @@
         {
             if (string.IsNullOrEmpty(columnLetter)) throw new ArgumentNullException("columnLetter");
 
-            columnLetter = columnLetter.ToUpperInvariant();
+            int retVal;
+            columnLetter = columnLetter.ToUpper();
+
+            //Extra check because we allow users to pass row col positions in as strings
+            if (columnLetter[0] <= '9')
+            {
+                retVal = Int32.Parse(columnLetter, NumberFormatForParse);
+                return retVal;
+            }
 
             int sum = 0;