--- a/src/pyams_media/zmi/templates/video-thumbnail.pt	Fri Oct 13 10:21:11 2017 +0200
+++ b/src/pyams_media/zmi/templates/video-thumbnail.pt	Mon Dec 11 15:29:06 2017 +0100
@@ -11,7 +11,7 @@
 					thumbnails extension:thumbnails(context);
 					conversions extension:conversions(context);
 					size thumbnails.get_image_size();"
-		tal:attributes="poster string:${href}/++thumb++${size[0]}x${size[1]}.png">
+		tal:attributes="poster string:${href}/++thumb++${size[0]}x${size[1]}.png?_=${view/timestamp}">
 		<tal:loop repeat="conversion conversions.get_conversions(order=('video/webm','video/mp4','video/x-flv'))">
 			<tal:if define="video_type extension:video_type(conversion);"
 					condition="video_type">