diff --git a/src/GEOMImpl/GEOMImpl_IGroupOperations.cxx b/src/GEOMImpl/GEOMImpl_IGroupOperations.cxx
index 224dda4aa..82d5a89b3 100644
--- a/src/GEOMImpl/GEOMImpl_IGroupOperations.cxx
+++ b/src/GEOMImpl/GEOMImpl_IGroupOperations.cxx
@@ -397,7 +397,8 @@ void GEOMImpl_IGroupOperations::DifferenceList (Handle(GEOM_Object) theGroup,
 
   Standard_Integer aLen = theSubShapes->Length();
   if (aLen < 1) {
-    SetErrorCode("The list is empty");
+    //SetErrorCode("The list is empty");
+    SetErrorCode(OK);
     return;
   }
 
@@ -414,8 +415,9 @@ void GEOMImpl_IGroupOperations::DifferenceList (Handle(GEOM_Object) theGroup,
   if (aSeq.IsNull()) return;
   Standard_Integer aLength = aSeq->Length();
 
-  if (aLength == 1 && aSeq->Value(1) == -1) // empty group
-    return;
+  // VSR 28/04/2011 commented to allow operation even for empty group
+  //   if (aLength == 1 && aSeq->Value(1) == -1) // empty group
+  //     return;
 
   TColStd_MapOfInteger mapIDsCurrent;
   Standard_Integer j = 1;
@@ -449,7 +451,7 @@ void GEOMImpl_IGroupOperations::DifferenceList (Handle(GEOM_Object) theGroup,
     // 1. If aShape_i is sub-shape of aMainShape - remove it
     if (mapIndices.Contains(aShape_i)) {
       rem_id = mapIndices.FindIndex(aShape_i);
-      if (mapIDsCurrent.Contains(rem_id)) {
+      if (rem_id > 0 && mapIDsCurrent.Contains(rem_id)) {
         mapIDsToRemove.Add(rem_id);
       }
     }
@@ -463,7 +465,7 @@ void GEOMImpl_IGroupOperations::DifferenceList (Handle(GEOM_Object) theGroup,
         TopoDS_Shape aSubShape_i = mapIndices_i.FindKey(ii);
         if (mapIndices.Contains(aSubShape_i)) {
           rem_id = mapIndices.FindIndex(aSubShape_i);
-          if (mapIDsCurrent.Contains(rem_id)) {
+          if (rem_id > 0 && mapIDsCurrent.Contains(rem_id)) {
             mapIDsToRemove.Add(rem_id);
           }
         }
@@ -476,7 +478,7 @@ void GEOMImpl_IGroupOperations::DifferenceList (Handle(GEOM_Object) theGroup,
         TopoDS_Shape aSubShape_i = aSubShapes_i.Current();
         if (mapIndices.Contains(aSubShape_i)) {
           rem_id = mapIndices.FindIndex(aSubShape_i);
-          if (mapIDsCurrent.Contains(rem_id)) {
+          if (rem_id > 0 && mapIDsCurrent.Contains(rem_id)) {
             mapIDsToRemove.Add(rem_id);
           }
         }
@@ -537,7 +539,8 @@ void GEOMImpl_IGroupOperations::UnionIDs (Handle(GEOM_Object) theGroup,
 
   Standard_Integer aLen = theSubShapes->Length();
   if (aLen < 1) {
-    SetErrorCode("The list is empty");
+    //SetErrorCode("The list is empty");
+    SetErrorCode(OK);
     return;
   }
 
@@ -629,7 +632,8 @@ void GEOMImpl_IGroupOperations::DifferenceIDs (Handle(GEOM_Object) theGroup,
 
   Standard_Integer aLen = theSubShapes->Length();
   if (aLen < 1) {
-    SetErrorCode("The list is empty");
+    //SetErrorCode("The list is empty");
+    SetErrorCode(OK);
     return;
   }
 
@@ -646,8 +650,9 @@ void GEOMImpl_IGroupOperations::DifferenceIDs (Handle(GEOM_Object) theGroup,
   if (aSeq.IsNull()) return;
   Standard_Integer aLength = aSeq->Length();
 
-  if (aLength == 1 && aSeq->Value(1) == -1) // empty group
-    return;
+  // VSR 28/04/2011 commented to allow operation even for empty group
+  //   if (aLength == 1 && aSeq->Value(1) == -1) // empty group
+  //     return;
 
   TColStd_MapOfInteger mapIDsCurrent;
   Standard_Integer j = 1;
@@ -672,21 +677,27 @@ void GEOMImpl_IGroupOperations::DifferenceIDs (Handle(GEOM_Object) theGroup,
   Standard_Integer i, rem_id;
   for (i = 1; i <= aLen; i++) {
     rem_id = theSubShapes->Value(i);
-    if (mapIDsCurrent.Contains(rem_id)) {
+    if (rem_id > 0 && mapIDsCurrent.Contains(rem_id)) {
       mapIDsToRemove.Add(rem_id);
     }
   }
 
   if (mapIDsToRemove.Extent() > 0) {
     Standard_Integer k = 1, aRemLength = mapIDsToRemove.Extent();
-    Handle(TColStd_HArray1OfInteger) aNewSeq = new TColStd_HArray1OfInteger(1, aLength - aRemLength);
-
-    for (j = 1; j <= aLength; j++) {
-      if (!mapIDsToRemove.Contains(aSeq->Value(j))) {
-        aNewSeq->SetValue(k, aSeq->Value(j));
-        k++;
+    Handle(TColStd_HArray1OfInteger) aNewSeq;
+    if ( aLength - aRemLength > 0 ) {
+      aNewSeq = new TColStd_HArray1OfInteger(1, aLength - aRemLength);
+      for (j = 1; j <= aLength; j++) {
+	if (!mapIDsToRemove.Contains(aSeq->Value(j))) {
+	  aNewSeq->SetValue(k, aSeq->Value(j));
+	  k++;
+	}
       }
     }
+    else {
+      aNewSeq = new TColStd_HArray1OfInteger(1,1);
+      aNewSeq->SetValue(1, -1);
+    }
 
     aSSI.SetIndices(aNewSeq);