diff --git a/lib/libufs/inode.c b/lib/libufs/inode.c
index 863e71867da..bc4d99c6620 100644
--- a/lib/libufs/inode.c
+++ b/lib/libufs/inode.c
@@ -48,6 +48,9 @@
 
 #include <libufs.h>
 
+_Static_assert(LIBUFS_MAXBSIZE >= MAXBSIZE,
+    "LIBUFS_MAXBSIZE must be at least MAXBSIZE");
+
 int
 getinode(struct uufsd *disk, union dinodep *dp, ino_t inum)
 {
diff --git a/lib/libufs/libufs.h b/lib/libufs/libufs.h
index bb92e082a87..b76d15b338b 100644
--- a/lib/libufs/libufs.h
+++ b/lib/libufs/libufs.h
@@ -29,6 +29,7 @@
 
 #ifndef	__LIBUFS_H__
 #define	__LIBUFS_H__
+
 #include <stdbool.h>
 
 /*
@@ -38,6 +39,8 @@
  */
 #define LIBUFS_BUFALIGN	128
 
+#define LIBUFS_MAXBSIZE	65536
+
 /*
  * userland ufs disk.
  */
@@ -48,11 +51,11 @@ struct uufsd {
 	} d_sbunion __aligned(LIBUFS_BUFALIGN);
 	union {
 		struct cg d_cg;		/* cylinder group */
-		char d_buf[MAXBSIZE];	/* cylinder group storage */
+		char d_buf[LIBUFS_MAXBSIZE]; /* cylinder group storage */
 	} d_cgunion __aligned(LIBUFS_BUFALIGN);
 	union {
 		union dinodep d_ino[1];	/* inode block */
-		char d_inos[MAXBSIZE];	/* inode block as buffer */
+		char d_inos[LIBUFS_MAXBSIZE]; /* inode block as buffer */
 	} d_inosunion __aligned(LIBUFS_BUFALIGN);
 	const char *d_name;		/* disk name */
 	const char *d_error;		/* human readable disk error */