Index: sys/fs/msdosfs/msdosfs_fat.c
===================================================================
--- sys/fs/msdosfs/msdosfs_fat.c
+++ sys/fs/msdosfs/msdosfs_fat.c
@@ -391,7 +391,7 @@
 	KASSERT((pmp->pm_inusemap[cn / N_INUSEBITS] & (1 << (cn % N_INUSEBITS)))
 	    == 0, ("Allocating used sector %ld %ld %x", cn, cn % N_INUSEBITS,
 		(unsigned)pmp->pm_inusemap[cn / N_INUSEBITS]));
-	pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
+	pmp->pm_inusemap[cn / N_INUSEBITS] |= 1U << (cn % N_INUSEBITS);
 	KASSERT(pmp->pm_freeclustercount > 0, ("usemap_alloc: too little"));
 	pmp->pm_freeclustercount--;
 	pmp->pm_flags |= MSDOSFS_FSIMOD;
@@ -412,7 +412,7 @@
 	KASSERT((pmp->pm_inusemap[cn / N_INUSEBITS] & (1 << (cn % N_INUSEBITS)))
 	    != 0, ("Freeing unused sector %ld %ld %x", cn, cn % N_INUSEBITS,
 		(unsigned)pmp->pm_inusemap[cn / N_INUSEBITS]));
-	pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1 << (cn % N_INUSEBITS));
+	pmp->pm_inusemap[cn / N_INUSEBITS] &= ~(1U << (cn % N_INUSEBITS));
 }
 
 int
@@ -775,7 +775,7 @@
 	for (cn = newst; cn <= pmp->pm_maxcluster;) {
 		idx = cn / N_INUSEBITS;
 		map = pmp->pm_inusemap[idx];
-		map |= (1 << (cn % N_INUSEBITS)) - 1;
+		map |= (1U << (cn % N_INUSEBITS)) - 1;
 		if (map != FULL_RUN) {
 			cn = idx * N_INUSEBITS + ffs(map ^ FULL_RUN) - 1;
 			if ((l = chainlength(pmp, cn, count)) >= count)
@@ -792,7 +792,7 @@
 	for (cn = 0; cn < newst;) {
 		idx = cn / N_INUSEBITS;
 		map = pmp->pm_inusemap[idx];
-		map |= (1 << (cn % N_INUSEBITS)) - 1;
+		map |= (1U << (cn % N_INUSEBITS)) - 1;
 		if (map != FULL_RUN) {
 			cn = idx * N_INUSEBITS + ffs(map ^ FULL_RUN) - 1;
 			if ((l = chainlength(pmp, cn, count)) >= count)
@@ -950,7 +950,7 @@
 
 	for (cn = pmp->pm_maxcluster + 1; cn < (pmp->pm_maxcluster +
 	    N_INUSEBITS) / N_INUSEBITS; cn++)
-		pmp->pm_inusemap[cn / N_INUSEBITS] |= 1 << (cn % N_INUSEBITS);
+		pmp->pm_inusemap[cn / N_INUSEBITS] |= 1U << (cn % N_INUSEBITS);
 
 	return (0);
 }