diff --git a/DesignspaceEditor2.roboFontExt/lib/designspaceEditor/locationPreview.py b/DesignspaceEditor2.roboFontExt/lib/designspaceEditor/locationPreview.py
index 4e22e28..5029f31 100644
--- a/DesignspaceEditor2.roboFontExt/lib/designspaceEditor/locationPreview.py
+++ b/DesignspaceEditor2.roboFontExt/lib/designspaceEditor/locationPreview.py
@@ -461,7 +461,8 @@ def designspaceEditorSourcesDidChangeSelection(self, notification):
         self.updatePreview()
 
     def roboFontDidSwitchCurrentGlyph(self, notification):
-        self.updatePreview()
+        if not self.w.getNSWindow().isKeyWindow():
+            self.updatePreview()
 
 
 if __name__ == '__main__':