diff --git a/components/fpdebug/fppascalparser.pas b/components/fpdebug/fppascalparser.pas
index ca2a78025f..1893f06542 100644
--- a/components/fpdebug/fppascalparser.pas
+++ b/components/fpdebug/fppascalparser.pas
@@ -2708,20 +2708,23 @@ begin
   if IsAdd then begin
     case tmp1.Kind of
       skPointer: ;
-      skInteger: Result := tmp1;
+      skInteger:  Result := tmp1;
       skCardinal: Result := tmp1;
+      skFloat:    Result := tmp1;
     end;
+    Result.AddReference{$IFDEF WITH_REFCOUNT_DEBUG}(@FValue, 'DoGetResultValue'){$ENDIF};
   end
   else begin
     case tmp1.Kind of
       skPointer: ;
-      skInteger: Result := TFpValueConstNumber.Create(-tmp1.AsInteger, True);
+      skInteger:  Result := TFpValueConstNumber.Create(-tmp1.AsInteger, True);
       skCardinal: Result := TFpValueConstNumber.Create(-tmp1.AsCardinal, True);
+      skFloat:    Result := TFpValueConstFloat.Create(-tmp1.AsFloat);
     end;
+    {$IFDEF WITH_REFCOUNT_DEBUG}if Result <> nil then Result.DbgRenameReference(nil, 'DoGetResultValue');{$ENDIF}
   end;
   {$POP}
 
- {$IFDEF WITH_REFCOUNT_DEBUG}if Result <> nil then Result.DbgRenameReference(nil, 'DoGetResultValue');{$ENDIF}
 end;
 
 { TFpPascalExpressionPartOperatorPlusMinus }
diff --git a/components/lazdebuggers/lazdebuggerfp/test/testwatches.pas b/components/lazdebuggers/lazdebuggerfp/test/testwatches.pas
index 6c3c3e801f..f92fea760d 100644
--- a/components/lazdebuggers/lazdebuggerfp/test/testwatches.pas
+++ b/components/lazdebuggers/lazdebuggerfp/test/testwatches.pas
@@ -2192,9 +2192,15 @@ begin
     t.Add('Const-Expr: ansistring ', '#A',    weAnsiStr('abc')).IgnKind.AddFlag(ehExpectError);
     t.Add('Const-Expr: ansistring ', '#$X',    weAnsiStr('abc')).IgnKind.AddFlag(ehExpectError);
 
+    t.Add('Const-Op: ', '10',     weInteger(10));
+    t.Add('Const-Op: ', '-10',     weInteger(-10));
+    t.Add('Const-Op: ', '- -10',     weInteger(10)); // 2 unary
+    t.Add('Const-Op: ', '+10',     weInteger(10));
+
     t.Add('Const-Op: ', '107 + 1',     weInteger(108));
     t.Add('Const-Op: ', '107 - 1',     weInteger(106));
     t.Add('Const-Op: ', '107 + -1',    weInteger(106));
+    t.Add('Const-Op: ', '107 + +1',    weInteger(108));
     t.Add('Const-Op: ', '107 - -1',    weInteger(108));
     t.Add('Const-Op: ', '11 * 3',      weInteger(33));
     t.Add('Const-Op: ', '11 * -3',     weInteger(-33));
@@ -2208,6 +2214,35 @@ begin
     t.Add('Const-bracket: ', '(1 + 11) * 3',      weInteger(36));
     t.Add('Const-bracket: ', '11 * (3 + 1)',      weInteger(44));
 
+    t.Add('Const-Op: ', '1.5',      weFloat(1.5));
+    t.Add('Const-Op: ', '-1.5',     weFloat(-1.5));
+    t.Add('Const-Op: ', '- -1.5',     weFloat(1.5));
+    t.Add('Const-Op: ', '+1.5',     weFloat(1.5));
+
+    t.Add('Const-Op: ', ' 10.5 + 1',      weFloat(11.5));
+    t.Add('Const-Op: ', ' 10.0 + 1',      weFloat(11));
+    t.Add('Const-Op: ', ' 10   + 1.5',    weFloat(11.5));
+    t.Add('Const-Op: ', '-10   + 1.5',    weFloat(-8.5));
+    t.Add('Const-Op: ', '-10   + -1.5',   weFloat(-11.5));
+
+    t.Add('Const-Op: ', ' 10.5 - 1',      weFloat(9.5));
+    t.Add('Const-Op: ', ' 10.0 - 1',      weFloat(9));
+    t.Add('Const-Op: ', ' 10   - 1.5',    weFloat(8.5));
+    t.Add('Const-Op: ', '-10   - 1.5',    weFloat(-11.5));
+    t.Add('Const-Op: ', '-10   - -1.5',   weFloat(-8.5));
+
+    t.Add('Const-Op: ', '10.5 * 3',      weFloat(31.5));
+    t.Add('Const-Op: ', '10.0 * 3',      weFloat(30));
+    t.Add('Const-Op: ', ' 9   * 1.5',    weFloat(13.5));
+    t.Add('Const-Op: ', '-9   * 1.5',    weFloat(-13.5));
+    t.Add('Const-Op: ', '-9   * -1.5',   weFloat(13.5));
+
+    t.Add('Const-Op: ', ' 31.5 / 3',      weFloat(10.5));
+    t.Add('Const-Op: ', ' 30.0 / 3',      weFloat(10));
+    t.Add('Const-Op: ', ' 13.5 / 1.5',    weFloat(9));
+    t.Add('Const-Op: ', '-13.5 / 1.5',    weFloat(-9));
+    t.Add('Const-Op: ', '-13.5 / -1.5',   weFloat(9));
+
     t.Add('Const-Op: ', '35 And 17',     weInteger(1));
     t.Add('Const-Op: ', '35 And 7',     weInteger(3));
     t.Add('Const-Op: ', '35 or 7',     weInteger(39));