diff --git a/ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/DateTimeUpDown/Implementation/DateTimeUpDown.cs b/ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/DateTimeUpDown/Implementation/DateTimeUpDown.cs
index 09699b42..c4c28e1e 100644
--- a/ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/DateTimeUpDown/Implementation/DateTimeUpDown.cs
+++ b/ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/DateTimeUpDown/Implementation/DateTimeUpDown.cs
@@ -85,6 +85,8 @@ namespace Microsoft.Windows.Controls
             if (string.IsNullOrEmpty(newValue))
                 throw new ArgumentException("CustomFormat should be specified.", FormatString);
 
+            _dateTimeParser.Format = newValue;
+
             InitializeDateTimeInfoListAndParseValue();
         }