diff --git a/ccid_common/cuart.c b/ccid_common/cuart.c
index bc99631..c617754 100644
--- a/ccid_common/cuart.c
+++ b/ccid_common/cuart.c
@@ -74,9 +74,8 @@
 	int etu_in_us = get_etu_in_us(cuart) + 1;
 	cuart->wtime_etu = cuart->wtime_etu ? cuart->wtime_etu : 1;
 
-	/* timemout is wtime * ETU + expected number of bytes * (12ETU+1 slack)ETU */
-	usecs = etu_in_us * cuart->wtime_etu +
-			etu_in_us * cuart->current_wtime_byte * (12+1);
+	/* timemout is wtime * ETU * expected number of bytes */
+	usecs = etu_in_us * cuart->wtime_etu * cuart->current_wtime_byte;
 
 	/* limit lower wait time to reasonable value */
 	usecs = usecs < 300000 ? 300000 : usecs;