diff --git a/src/client/qwaylandshmbackingstore.cpp b/src/client/qwaylandshmbackingstore.cpp
index 3fe2ce80..6d660e64 100644
--- a/src/client/qwaylandshmbackingstore.cpp
+++ b/src/client/qwaylandshmbackingstore.cpp
@@ -289,11 +289,13 @@ void QWaylandShmBackingStore::resize(const QSize &size)
         buffer = getBuffer(sizeWithMargins);
     }
 
-    qsizetype oldSize = mBackBuffer ? mBackBuffer->image()->sizeInBytes() : 0;
+    qsizetype oldSizeInBytes = mBackBuffer ? mBackBuffer->image()->sizeInBytes() : 0;
+    qsizetype newSizeInBytes = buffer->image()->sizeInBytes();
+
     // mBackBuffer may have been deleted here but if so it means its size was different so we wouldn't copy it anyway
-    if (mBackBuffer != buffer && oldSize == buffer->image()->sizeInBytes()) {
-        memcpy(buffer->image()->bits(), mBackBuffer->image()->constBits(), buffer->image()->sizeInBytes());
-    }
+   if (mBackBuffer != buffer && oldSizeInBytes == newSizeInBytes)
+        memcpy(buffer->image()->bits(), mBackBuffer->image()->constBits(), newSizeInBytes);
+
     mBackBuffer = buffer;
     // ensure the new buffer is at the beginning of the list so next time getBuffer() will pick
     // it if possible
@@ -302,8 +304,9 @@ void QWaylandShmBackingStore::resize(const QSize &size)
         mBuffers.prepend(buffer);
     }
 
-    if (windowDecoration() && window()->isVisible())
+    if (windowDecoration() && window()->isVisible() && oldSizeInBytes != newSizeInBytes) {
         windowDecoration()->update();
+    }
 }
 
 QImage *QWaylandShmBackingStore::entireSurface() const