diff --git a/samples/propgrid/propgrid.cpp b/samples/propgrid/propgrid.cpp
index 3449f98c83..c76a07df30 100644
--- a/samples/propgrid/propgrid.cpp
+++ b/samples/propgrid/propgrid.cpp
@@ -2472,8 +2472,7 @@ void FormMain::OnFitColumnsClick( wxCommandEvent& WXUNUSED(event) )
     int dx = oldFullSize.x - oldGridSize.x;
     int dy = oldFullSize.y - oldGridSize.y;
 
-    newSz.x += dx;
-    newSz.y += dy;
+    newSz.IncBy(dx, dy);
 
     SetSize(newSz);
 }
diff --git a/samples/propgrid/tests.cpp b/samples/propgrid/tests.cpp
index 1d36106966..a5807dbd04 100644
--- a/samples/propgrid/tests.cpp
+++ b/samples/propgrid/tests.cpp
@@ -1211,8 +1211,7 @@ bool FormMain::RunTests( bool fullTest, bool interactive )
 
         wxSize sz = GetSize();
         wxSize origSz = sz;
-        sz.x += 5;
-        sz.y += 5;
+        sz.IncBy(5, 5);
 
         if ( pgman->GetGrid()->GetSplitterPosition() != trySplitterPos )
             RT_FAILURE_MSG(wxString::Format(wxT("Splitter position was %i (should have been %i)"),(int)pgman->GetGrid()->GetSplitterPosition(),trySplitterPos).c_str());