diff --git a/sys/fs/msdosfs/bpb.h b/sys/fs/msdosfs/bpb.h
index d5b86a734276..1374c9ae7564 100644
--- a/sys/fs/msdosfs/bpb.h
+++ b/sys/fs/msdosfs/bpb.h
@@ -101,7 +101,7 @@ struct bpb710 {
 #define	putulong(p, v)	(*((u_int32_t *)(p)) = (v))
 #else
 #define getushort(x)	(((u_int8_t *)(x))[0] + (((u_int8_t *)(x))[1] << 8))
-#define getulong(x)	(((u_int8_t *)(x))[0] + (((u_int8_t *)(x))[1] << 8) \
+#define getulong(x)	(u_int32_t)(((u_int8_t *)(x))[0] + (((u_int8_t *)(x))[1] << 8) \
 			 + (((u_int8_t *)(x))[2] << 16)	\
 			 + (((u_int8_t *)(x))[3] << 24))
 #define putushort(p, v)	(((u_int8_t *)(p))[0] = (v),	\