diff --git a/src/pv/transfer.c b/src/pv/transfer.c
index a4823ae..5971815 100644
--- a/src/pv/transfer.c
+++ b/src/pv/transfer.c
@@ -349,8 +349,12 @@ static int pv__transfer_read(pvstate_t state, int fd, bool *eof_in, bool *eof_ou
 	 */
 	if (state->control.stop_at_size && !state->control.linemode) {
 		off_t bytes_remaining_to_read = state->control.size - state->transfer.total_bytes_read;
-		if (bytes_can_read > (size_t) bytes_remaining_to_read)
+		if (bytes_can_read > (size_t) bytes_remaining_to_read) {
+			debug("%lld > (%lld-%lld=%lld): %s", (long long) bytes_can_read,
+			      (long long) (state->control.size), (long long) state->transfer.total_bytes_read,
+			      (long long) bytes_remaining_to_read, "truncating for stop-at-size");
 			bytes_can_read = (size_t) bytes_remaining_to_read;
+		}
 	}
 
 	nread = 0;