diff --git a/check/main.c b/check/main.c
index db055ae19..96c7ef7d8 100644
--- a/check/main.c
+++ b/check/main.c
@@ -87,6 +87,7 @@ bool is_free_space_tree = false;
 bool init_extent_tree = false;
 bool check_data_csum = false;
 static bool found_free_ino_cache = false;
+static bool found_unknown_key = false;
 struct cache_tree *roots_info_cache = NULL;
 
 enum btrfs_check_mode {
@@ -1895,6 +1896,10 @@ static int process_one_leaf(struct btrfs_root *root, struct extent_buffer *eb,
 			ret = process_xattr_item(eb, i, &key, active_node);
 			break;
 		default:
+			error("Unknown key (%llu %u %llu) found in leaf %llu",
+			      key.objectid, key.type, key.offset,
+			      eb->start);
+			found_unknown_key = true;
 			break;
 		};
 	}
@@ -4027,6 +4032,8 @@ static int check_fs_roots(struct cache_tree *root_cache)
 		free_extent_cache_tree(&wc.shared);
 	if (!cache_tree_empty(&wc.shared))
 		fprintf(stderr, "warning line %d\n", __LINE__);
+	if (!err && found_unknown_key)
+		err = 1;
 
 	return err;
 }
diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c
index ea4d40178..8a4c5bc1e 100644
--- a/check/mode-lowmem.c
+++ b/check/mode-lowmem.c
@@ -2808,8 +2808,9 @@ static int check_inode_item(struct btrfs_root *root, struct btrfs_path *path)
 		case BTRFS_XATTR_ITEM_KEY:
 			break;
 		default:
-			error("ITEM[%llu %u %llu] UNKNOWN TYPE",
-			      key.objectid, key.type, key.offset);
+			error("ITEM[%llu %u %llu] UNKNOWN TYPE in leaf %llu",
+			      key.objectid, key.type, key.offset, node->start);
+			err |= UNKNOWN_KEY;
 		}
 	}
 
diff --git a/check/mode-lowmem.h b/check/mode-lowmem.h
index cd0355465..ec199b4c8 100644
--- a/check/mode-lowmem.h
+++ b/check/mode-lowmem.h
@@ -48,6 +48,7 @@
 #define INVALID_GENERATION	(1U << 26)	/* Generation is too new */
 #define SUPER_BYTES_USED_ERROR	(1U << 27)	/* Super bytes_used is invalid */
 #define DUP_FILENAME_ERROR	(1U << 28)	/* DIR_ITEM contains duplicate names */
+#define UNKNOWN_KEY		(1U << 29)	/* Found unknown key type in fs trees */
 
 /*
  * Error bit for low memory mode check.
diff --git a/tests/fsck-tests/069-unknown-fs-tree-key/test.sh b/tests/fsck-tests/069-unknown-fs-tree-key/test.sh
new file mode 100755
index 000000000..ea4f04e28
--- /dev/null
+++ b/tests/fsck-tests/069-unknown-fs-tree-key/test.sh
@@ -0,0 +1,14 @@
+#!/bin/bash
+#
+# Verify that check can report unknown key types in subvolume trees
+
+source "$TEST_TOP/common" || exit
+
+check_prereq btrfs
+
+check_image() {
+	run_mustfail "unknown keys in subvolume trees not reported as error" \
+		"$TOP/btrfs" check "$1"
+}
+
+check_all_images
diff --git a/tests/fsck-tests/069-unknown-fs-tree-key/unknown_key_empty.img.xz b/tests/fsck-tests/069-unknown-fs-tree-key/unknown_key_empty.img.xz
new file mode 100644
index 000000000..300a7cc92
Binary files /dev/null and b/tests/fsck-tests/069-unknown-fs-tree-key/unknown_key_empty.img.xz differ