diff --git a/stand/libsa/dosfs.c b/stand/libsa/dosfs.c
--- a/stand/libsa/dosfs.c
+++ b/stand/libsa/dosfs.c
@@ -155,7 +155,7 @@
 static int fatcnt(DOS_FS *, u_int);
 static int fatget(DOS_FS *, u_int *);
 static int fatend(u_int, u_int);
-static int ioread(DOS_FS *, u_int, void *, size_t);
+static int ioread(DOS_FS *, size_t, void *, size_t);
 static int ioget(struct open_file *, daddr_t, void *, size_t);
 
 static int
@@ -405,7 +405,7 @@
 		}
 		if (!clus || (n = f->fs->bsize - off) > cnt)
 			n = cnt;
-		if ((err = ioread(f->fs, (c ? blkoff(f->fs, c) :
+		if ((err = ioread(f->fs, (c ? blkoff(f->fs, (size_t)c) :
 		    secbyt(f->fs->lsndir)) + off, buf, n)))
 			goto out;
 		f->offset += n;
@@ -911,10 +911,10 @@
  * Offset-based I/O primitive
  */
 static int
-ioread(DOS_FS *fs, u_int offset, void *buf, size_t nbyte)
+ioread(DOS_FS *fs, size_t offset, void *buf, size_t nbyte)
 {
 	char *s;
-	u_int off, n;
+	size_t off, n;
 	int err;
 	u_char local_buf[SECSIZ];