diff --git a/core/src/web/filesystem.ts b/core/src/web/filesystem.ts
index 3e9985832..ce27dca3c 100644
--- a/core/src/web/filesystem.ts
+++ b/core/src/web/filesystem.ts
@@ -202,11 +202,12 @@ export class FilesystemPluginWeb extends WebPlugin implements FilesystemPlugin {
 
     let parentEntry = await this.dbRequest('get', [parentPath]) as EntryObj;
     if (parentEntry === undefined) {
-      const parentArgPathIndex = parentPath.indexOf('/', 1);
-      const parentArgPath = parentArgPathIndex !== -1 ? parentPath.substr(parentArgPathIndex) : '/';
-      await this.mkdir({path: parentArgPath, directory: options.directory, recursive: true});
+      const subDirIndex = parentPath.indexOf('/', 1);
+      if (subDirIndex !== -1) {
+        const parentArgPath = parentPath.substr(subDirIndex);
+        await this.mkdir({path: parentArgPath, directory: options.directory, recursive: true});
+      }
     }
-
     if (occupiedEntry !== undefined) {
       data = occupiedEntry.content + data;
       ctime = occupiedEntry.ctime;