diff --git a/source/fs/mufs/dir.c b/source/fs/mufs/dir.c
index 9843761..dab058a 100644
--- a/source/fs/mufs/dir.c
+++ b/source/fs/mufs/dir.c
@@ -226,7 +226,6 @@ size_t read_dirent(struct mufs *fs, struct mufs_tree *tree,
 size_t write_dirent(struct mufs_tree *tree,
 	uint32_t va, struct mufs_dirent *dirent)
 {
-	struct mufs_dtree dtree;
 	struct mufs_dentry entry;
 
 	entry.type = dirent->type;
@@ -242,13 +241,10 @@ size_t write_dirent(struct mufs_tree *tree,
 	if (mufs_tree_write(tree, &entry, va, sizeof entry) == 0)
 		return 0;
 
-	tree->file_size = max(tree->file_size, va + sizeof entry + entry.path_len);
+	va += sizeof entry + entry.path_len;
+	tree->file_size = max(tree->file_size, va);
 
-	dtree.file_size = tree->file_size;
-	dtree.root = tree->root;
-	dtree.depth = tree->depth;
-
-	if (flash_write(tree->fs->dev, tree->va, &dtree, sizeof dtree) == 0)
+	if (tree->file_size <= va && mufs_sync_tree(tree) < 0)
 		return 0;
 
 	return entry.path_len + sizeof entry;
diff --git a/source/fs/mufs/file.c b/source/fs/mufs/file.c
index 60a24be..a08beaf 100644
--- a/source/fs/mufs/file.c
+++ b/source/fs/mufs/file.c
@@ -90,17 +90,8 @@ size_t mufs_write(struct mufs_file *file, const void *data, size_t len)
 
 	file->va += ret;
 
-	if (file->tree->file_size <= file->va) {
-		struct mufs_dtree dtree;
-
-		dtree.file_size = file->tree->file_size;
-		dtree.root = file->tree->root;
-		dtree.depth = file->tree->depth;
-
-		if (flash_write(file->fs->dev, file->tree->va, &dtree,
-			sizeof dtree) == 0)
-			return 0;
-	}
+	if (file->tree->file_size <= file->va && mufs_sync_tree(file->tree) < 0)
+		return 0;
 
 	return ret;
 }
diff --git a/source/fs/mufs/tree.c b/source/fs/mufs/tree.c
index ae34a2e..3e31293 100644
--- a/source/fs/mufs/tree.c
+++ b/source/fs/mufs/tree.c
@@ -9,6 +9,7 @@
 #include <fs/mufs.h>
 
 #include "block.h"
+#include "dir.h"
 #include "tree.h"
 
 static int mufs_do_lookup(struct mufs *fs, uint32_t *page,
@@ -254,3 +255,19 @@ size_t mufs_tree_write(struct mufs_tree *tree, void *data,
 
 	return nbytes;
 }
+
+int mufs_sync_tree(struct mufs_tree *tree)
+{
+	struct mufs *fs = tree->fs;
+	struct flash_dev *dev = fs->dev;
+	struct mufs_dtree dtree;
+
+	dtree.file_size = tree->file_size;
+	dtree.root = tree->root;
+	dtree.depth = tree->depth;
+
+	if (flash_write(dev, tree->va, &dtree, sizeof dtree) == 0)
+		return -1;
+
+	return 0;
+}
diff --git a/source/fs/mufs/tree.h b/source/fs/mufs/tree.h
index 10d554f..39c3602 100644
--- a/source/fs/mufs/tree.h
+++ b/source/fs/mufs/tree.h
@@ -11,3 +11,4 @@ size_t mufs_tree_read(struct mufs_tree *tree, void *data, uint32_t va,
 	size_t len);
 size_t mufs_tree_write(struct mufs_tree *tree, void *data, uint32_t va,
 	size_t len);
+int mufs_sync_tree(struct mufs_tree *tree);