diff --git a/lcl/interfaces/gtk2/gtk2def.pp b/lcl/interfaces/gtk2/gtk2def.pp
index 656e46c729..6197be1565 100644
--- a/lcl/interfaces/gtk2/gtk2def.pp
+++ b/lcl/interfaces/gtk2/gtk2def.pp
@@ -451,10 +451,14 @@ type
     wwiInvalidEvent,                  // special mark for widgetinfo
                                       // see gtkchanged_editbox and
                                       // gtkchanged_editbox_backspace in gtkcallback.inc
-    wwiTabWidgetFocusCheck            // TabWidget have nasty behaviour when clicked
+    wwiTabWidgetFocusCheck,           // TabWidget have nasty behaviour when clicked
                                       // by mouse: switches focus here and there, so
                                       // focused control triggers OnExit and it looks
                                       // like it triggered OnEnter.issue #20493
+    wwiClientRectWhilePendingSize     // A wrong clientrect may have been returned.
+                                      // The LCL asks for clientrect, while a resize
+                                      // request was pending. The LCL would have
+                                      // expected a value for the new size;
     );
   TWidgetInfoFlags = set of TWidgetInfoFlag;
   tGtkStateEnumRange = 0..31;
diff --git a/lcl/interfaces/gtk2/gtk2proc.inc b/lcl/interfaces/gtk2/gtk2proc.inc
index 4dc113c784..bab92d65c6 100644
--- a/lcl/interfaces/gtk2/gtk2proc.inc
+++ b/lcl/interfaces/gtk2/gtk2proc.inc
@@ -4670,6 +4670,7 @@ function GetWidgetClientRect(TheWidget: PGtkWidget): TRect;
 var
   Widget, ClientWidget: PGtkWidget;
   AChild: PGtkWidget;
+  WidgetInfo: PWidgetInfo;
 
   procedure GetNoteBookClientRect(NBWidget: PGtkNotebook);
   var
@@ -4707,6 +4708,12 @@ begin
   Result := Rect(0, 0, 0, 0);
   Widget := TheWidget;
   ClientWidget := GetFixedWidget(Widget);
+
+  if FWidgetsWithResizeRequest.Contains(Widget) then begin
+    WidgetInfo := GetWidgetInfo(Widget);
+    if WidgetInfo <> nil then include(WidgetInfo^.Flags, wwiClientRectWhilePendingSize);
+  end;
+
   if (ClientWidget <> nil) then
     Widget := ClientWidget;
   if (Widget <> nil) then
@@ -6643,6 +6650,8 @@ var
   end;
     
   procedure UpdateLCLSize;
+  var
+    WidgetInfo: PWidgetInfo;
   begin
     LCLWidth:=LCLControl.Width;
     LCLHeight:=LCLControl.Height;
@@ -6651,6 +6660,11 @@ var
       WidthHeightChanged:=true;
       //DebugLn(['UpdateLCLSize InvalidateClientRectCache ',DbgSName(LCLControl)]);
       LCLControl.InvalidateClientRectCache(false);
+    end
+    else begin
+      WidgetInfo := GetWidgetInfo(aWidget);
+      if (WidgetInfo <> nil) and (wwiClientRectWhilePendingSize in WidgetInfo^.Flags) then
+        LCLControl.InvalidateClientRectCache(false);
     end;
   end;
 
diff --git a/lcl/interfaces/gtk2/gtk2widgetset.inc b/lcl/interfaces/gtk2/gtk2widgetset.inc
index 44e6fac178..0c3df25736 100644
--- a/lcl/interfaces/gtk2/gtk2widgetset.inc
+++ b/lcl/interfaces/gtk2/gtk2widgetset.inc
@@ -2277,6 +2277,7 @@ procedure TGtk2WidgetSet.SendCachedLCLMessages;
     IsTopLevelWidget: boolean;
     TopologicalList: TFPList; // list of PGtkWidget;
     i: integer;
+    WidgetInfo: PWidgetInfo;
 
     procedure RaiseWidgetWithoutControl;
     begin
@@ -2322,6 +2323,8 @@ procedure TGtk2WidgetSet.SendCachedLCLMessages;
         SetWindowSizeAndPosition(PgtkWindow(Widget),TWinControl(LCLControl));
       end;
 
+      WidgetInfo := GetWidgetInfo(Widget);
+      if WidgetInfo <> nil then exclude(WidgetInfo^.Flags, wwiClientRectWhilePendingSize);
     end;
     TopologicalList.Free;
     FWidgetsWithResizeRequest.Clear;