diff --git a/src/TDF/TDF_CopyLabel.cxx b/src/TDF/TDF_CopyLabel.cxx
index 745e7e1905..824f788bfa 100755
--- a/src/TDF/TDF_CopyLabel.cxx
+++ b/src/TDF/TDF_CopyLabel.cxx
@@ -97,13 +97,16 @@ void TDF_CopyLabel::ExternalReferences(const TDF_Label& aRefLabel, const TDF_Lab
 
 //       TDF_Tool::Entry(att->Label(), entr1);  
 //       cout<<"\t\tReferences attribute dynamic type = "<<att->DynamicType()<<" Label = "<<entr1 <<endl;
-      if (aFilter.IsKept(att) && att->Label().IsDifferent(aRefLabel) &&
-	  !att->Label().IsDescendant(aRefLabel)) {
-	aExternals.Add(att);
-	extRefFound = Standard_True;
+      if (!att.IsNull() && !att->Label().IsNull())
+      {
+        if (aFilter.IsKept(att) && att->Label().IsDifferent(aRefLabel) &&
+	    !att->Label().IsDescendant(aRefLabel)) {
+          aExternals.Add(att);
+	  extRefFound = Standard_True;
+        }
       }
     }
-
+    
 //     const TDF_LabelMap& labMap = ds->Labels();
 //     for (TDF_MapIteratorOfLabelMap labMItr(labMap);labMItr.More(); labMItr.Next()) {
 //       TDF_Tool::Entry(labMItr.Key(), entr1);  
diff --git a/src/TDF/TDF_Tool.cxx b/src/TDF/TDF_Tool.cxx
index bc78cd5c12..740d563a88 100755
--- a/src/TDF/TDF_Tool.cxx
+++ b/src/TDF/TDF_Tool.cxx
@@ -181,9 +181,12 @@ static Standard_Boolean TDF_Tool_DescendantRef
 	// CLE
 	// const Handle(TDF_Attribute)& att = attMItr.Key();
 	Handle(TDF_Attribute) att = attMItr.Key();
-	// ENDCLE
-	if (aFilter.IsKept(att) && !att->Label().IsDescendant(aRefLabel))
-	  return Standard_False;
+        if (!att.IsNull() && !att->Label().IsNull())
+        {
+	  // ENDCLE
+	  if (aFilter.IsKept(att) && !att->Label().IsDescendant(aRefLabel))
+	    return Standard_False;
+        }
       }
       ds->Clear();
     }
diff --git a/tests/bugs/caf/bug23799 b/tests/bugs/caf/bug23799
new file mode 100755
index 0000000000..4da857ea6d
--- /dev/null
+++ b/tests/bugs/caf/bug23799
@@ -0,0 +1,25 @@
+puts "============"
+puts "OCC23799"
+puts "============"
+puts ""
+#######################################################################
+# Crash on copying a label
+#######################################################################
+
+set BugNumber OCC23799
+
+# Create a new document
+NewDocument D
+
+psphere s 100
+explode s f
+
+ImportShape D 0:1 s
+SelectShape D 0:2 s_1 s
+ForgetAll D 0:1
+
+if { [catch [CopyLabel D 0:2 0:3] ] != 0 } {
+  puts "${BugNumber}: Error copy label"
+} else {
+  puts "${BugNumber}: OK"
+}
diff --git a/tests/bugs/moddata_1/bug22623 b/tests/bugs/moddata_1/bug22623
index f75dcca1ef..0c28310dc5 100755
--- a/tests/bugs/moddata_1/bug22623
+++ b/tests/bugs/moddata_1/bug22623
@@ -1,5 +1,6 @@
 puts "TODO ?#22623 ALL: \\*\\* Exception"
 puts "TODO ?#22623 ALL: An exception was caught"
+puts "TODO ?#22623 ALL: TEST INCOMPLETE"
 
 puts "============"
 puts "OCC22623"