diff --git a/src/dj.c b/src/dj.c
index 7b3bb0a..e65274a 100644
--- a/src/dj.c
+++ b/src/dj.c
@@ -69,16 +69,19 @@ static int write_flags = O_WRONLY | O_CREAT;
 
 static struct Io *
 Io_read(struct Io *io){
+	int t;
 
 	assert(io->bs > 0);
+	assert(io->bufuse < io->bs);
 
-	io->bytes += (io->bufuse = read(io->fd, &(io->buf)[io->bufuse],
+	io->bufuse += (t = read(io->fd, &(io->buf)[io->bufuse],
 		io->bs - io->bufuse));
 
 	assert(io->bufuse <= io->bs);
 
-	io->prec += (0 < io->bufuse && io->bufuse < io->bs);
-	io->rec  += (io->bufuse == io->bs);
+	io->bytes += t;
+	io->prec  += (0 < io->bufuse && io->bufuse < io->bs);
+	io->rec   += (io->bufuse == io->bs);
 
 	return io;
 }
@@ -94,8 +97,8 @@ Io_write(struct Io *io){
 		memmove(io->buf, &(io->buf)[t], (io->bufuse -= t));
 
 	io->bytes += t;
-	io->prec  += (t > 0 && io->bufuse > 0);
-	io->rec   += (t > 0 && io->bufuse == 0);
+	io->prec  += (0 < io->bufuse && 0 < t);
+	io->rec   += (io->bufuse == 0 && 0 < t);
 
 	return io;
 }