diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index cc89cff029e1..5f6af0870dfd 100644
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -1253,7 +1253,7 @@ static void vsc9959_tas_guard_bands_update(struct ocelot *ocelot, int port)
 	/* Consider the standard Ethernet overhead of 8 octets preamble+SFD,
 	 * 4 octets FCS, 12 octets IFG.
 	 */
-	needed_bit_time_ps = (maxlen + 24) * picos_per_byte;
+	needed_bit_time_ps = (u64)(maxlen + 24) * picos_per_byte;
 
 	dev_dbg(ocelot->dev,
 		"port %d: max frame size %d needs %llu ps at speed %d\n",