diff --git a/src/common.ts b/src/common.ts
index 5f7b15e5..a6554862 100644
--- a/src/common.ts
+++ b/src/common.ts
@@ -54,7 +54,8 @@ export async function getProjects(api: Api, groups: number[]): Promise<Project[]
  * @param arr Flattened array
  */
 export function flatten2dArray<T>(arr: T[][]): T[] {
-  return [].concat.apply([], arr);
+  // TODO: fix this
+  return [].concat.apply([], arr as any);
 }
 
 /**