diff --git a/Interfaces/ZUGFeRDInterface.vb b/Interfaces/ZUGFeRDInterface.vb
index f2bc7431..75c4bc15 100644
--- a/Interfaces/ZUGFeRDInterface.vb
+++ b/Interfaces/ZUGFeRDInterface.vb
@@ -103,11 +103,15 @@ Public Class ZUGFeRDInterface
     End Sub
 
     Public Function FilterPropertyMap(pPropertyMap As Dictionary(Of String, XmlItemProperty), pSpecification As String) As Dictionary(Of String, XmlItemProperty)
+        _logger.Debug("Filtering Property map for Specification [{0}]", pSpecification)
+
         If pSpecification = ZUGFERD_SPEC_10 Then
+            _logger.Debug("Special Case [{0}], including [{1}]", ZUGFERD_SPEC_10, ZUGFERD_SPEC_DEFAULT)
             Return pPropertyMap.
                 Where(Function(kv) kv.Value.Specification = pSpecification Or kv.Value.Specification = ZUGFERD_SPEC_DEFAULT).
                 ToDictionary(Function(kv) kv.Key, Function(kv) kv.Value)
         Else
+            _logger.Debug("Using Specification [{0}]", pSpecification)
             Return pPropertyMap.
                 Where(Function(kv) kv.Value.Specification = pSpecification).
                 ToDictionary(Function(kv) kv.Key, Function(kv) kv.Value)