diff --git a/python/plugins/db_manager/layer_preview.py b/python/plugins/db_manager/layer_preview.py
index 74042ff6d21..8944fec669d 100644
--- a/python/plugins/db_manager/layer_preview.py
+++ b/python/plugins/db_manager/layer_preview.py
@@ -54,10 +54,12 @@ class LayerPreview(QgsMapCanvas):
     def loadPreview(self, item):
         if item == self.item and not self.dirty:
             return
-        self._clear()
+
         if item is None:
             return
 
+        self._clear()
+
         if isinstance(item, Table) and item.type in [Table.VectorType, Table.RasterType]:
             # update the preview, but first let the manager chance to show the canvas
             runPrev = lambda: self._loadTablePreview(item)