diff --git a/harbour/ChangeLog b/harbour/ChangeLog
index 92dfbc560d..1ead860627 100644
--- a/harbour/ChangeLog
+++ b/harbour/ChangeLog
@@ -8,6 +8,15 @@
    2002-12-01 13:30 UTC+0100 Foo Bar <foo.bar@foobar.org>
 */
 
+2007-06-03 23:03 UTC+0300 Mindaugas Kavaliauskas (dbtopas/at/dbtopas.lt)
+  * harbour/include/hbexprop.h
+  * harbour/include/hbexprb.c
+  * harbour/source/common/expropt2.c
+     * added UPPER("") optimisation. The side effect of this modification 
+       is that Harbour becomes Clipper bug compatible in calculation of 
+       AT(UPPER(""), "test"). Though this optimisation does not introduce 
+       any buggy behaviour itself.
+
 2007-06-02 12:30 UTC+0200 Enrico Maria Giordano (e.m.giordano@emagsoftware.it)
   * harbour/contrib/hbzlib
      * replaced with the one borrowed from xharbour, source modifications by Przemek
diff --git a/harbour/include/hbexprb.c b/harbour/include/hbexprb.c
index 0014a029e1..a2fc70f664 100644
--- a/harbour/include/hbexprb.c
+++ b/harbour/include/hbexprb.c
@@ -1581,6 +1581,10 @@ static HB_EXPR_FUNC( hb_compExprUseFunCall )
                   if( HB_SUPPORT_HARBOUR )
                      hb_compExprReduceSTOD( pSelf, usCount, HB_COMP_PARAM );
                }
+               else if( ( strcmp( "UPPER", pName->value.asSymbol ) == 0 ) && usCount )
+               {
+                  hb_compExprReduceUPPER( pSelf, HB_COMP_PARAM );
+               }
             }
          }
          break;
diff --git a/harbour/include/hbexprop.h b/harbour/include/hbexprop.h
index 1398ed3c40..b7e891581c 100644
--- a/harbour/include/hbexprop.h
+++ b/harbour/include/hbexprop.h
@@ -195,6 +195,7 @@ extern BOOL hb_compExprReduceCHR( HB_EXPR_PTR, HB_COMP_DECL );
 extern BOOL hb_compExprReduceLEN( HB_EXPR_PTR, HB_COMP_DECL );
 extern BOOL hb_compExprReduceASC( HB_EXPR_PTR, HB_COMP_DECL );
 extern BOOL hb_compExprReduceSTOD( HB_EXPR_PTR pSelf, USHORT usCount, HB_COMP_DECL );
+extern BOOL hb_compExprReduceUPPER( HB_EXPR_PTR, HB_COMP_DECL );
 
 HB_EXTERN_END
 
diff --git a/harbour/source/common/expropt2.c b/harbour/source/common/expropt2.c
index 727adc5065..0615e0b442 100644
--- a/harbour/source/common/expropt2.c
+++ b/harbour/source/common/expropt2.c
@@ -1436,3 +1436,27 @@ BOOL hb_compExprReduceSTOD( HB_EXPR_PTR pSelf, USHORT usCount, HB_COMP_DECL )
 
    return FALSE;
 }
+
+BOOL hb_compExprReduceUPPER( HB_EXPR_PTR pSelf, HB_COMP_DECL )
+{
+   HB_EXPR_PTR pParms = pSelf->value.asFunCall.pParms;
+   HB_EXPR_PTR pArg = pParms->value.asList.pExprList;
+
+   if( pArg->ExprType == HB_ET_STRING && pArg->ulLength == 0 )
+   {
+      HB_EXPR_PTR pExpr = HB_COMP_EXPR_NEW( HB_ET_STRING );
+
+      pExpr->ValType = HB_EV_STRING;
+      pExpr->value.asString.string = "";
+      pExpr->value.asString.dealloc = FALSE;
+      pExpr->ulLength = 0;
+
+      HB_COMP_EXPR_FREE( pParms );
+      HB_COMP_EXPR_FREE( pSelf->value.asFunCall.pFunName );
+      memcpy( pSelf, pExpr, sizeof( HB_EXPR ) );
+      HB_COMP_EXPR_CLEAR( pExpr );
+      return TRUE;
+   }
+   return FALSE;
+}
+