diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index 8345a2b2d05b..2e8b1a489c20 100644
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -903,6 +903,8 @@ unsigned bcachefs_metadata_required_upgrade_below = bcachefs_metadata_version_re
 #define BCH_SB_SECTOR			8
 #define BCH_SB_MEMBERS_MAX		64 /* XXX kill */
 
+#define BCH_SB_LAYOUT_SIZE_BITS_MAX	16 /* 32 MB */
+
 struct bch_sb_layout {
 	__uuid_t		magic;	/* bcachefs superblock UUID */
 	__u8			layout_type;
diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index e7527d551e3c..989d16bba8f0 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -649,7 +649,7 @@ reread:
 
 	bytes = vstruct_bytes(sb->sb);
 
-	if (bytes > 512 << sb->sb->layout.sb_max_size_bits) {
+	if (bytes > 512ULL << min(BCH_SB_LAYOUT_SIZE_BITS_MAX, sb->sb->layout.sb_max_size_bits)) {
 		prt_printf(err, "Invalid superblock: too big (got %zu bytes, layout max %lu)",
 		       bytes, 512UL << sb->sb->layout.sb_max_size_bits);
 		return -BCH_ERR_invalid_sb_too_big;