diff --git a/src/util/file_reader.ts b/src/util/file_reader.ts
index 2ed3b5ee..d8beeeb1 100644
--- a/src/util/file_reader.ts
+++ b/src/util/file_reader.ts
@@ -17,7 +17,7 @@ export type FileSource = {
 
 export type FileSources = FileSource[];
 
-export async function collectCustomBehaviors(sources: string[]) {
+export async function collectCustomBehaviors(sources: string[]): Promise<FileSources> {
   const collectedSources: FileSources = [];
 
   for (const fileSource of sources) {
@@ -33,7 +33,7 @@ export async function collectCustomBehaviors(sources: string[]) {
   return collectedSources;
 }
 
-async function collectOnlineBehavior(url: string) {
+async function collectOnlineBehavior(url: string): Promise<FileSources> {
   const filename = crypto.randomBytes(4).toString("hex") + ".js";
   const behaviorFilepath = `/app/behaviors/${filename}`;
 
@@ -57,7 +57,7 @@ async function collectOnlineBehavior(url: string) {
   return [];
 }
 
-async function collectLocalPathBehaviors(fileOrDir: string, depth = 0) {
+async function collectLocalPathBehaviors(fileOrDir: string, depth = 0): Promise<FileSources> {
   const resolvedPath = path.resolve(fileOrDir);
 
   if (depth >= MAX_DEPTH) {
@@ -83,7 +83,7 @@ async function collectLocalPathBehaviors(fileOrDir: string, depth = 0) {
 
   if (stat.isDirectory()) {
     const files = await fsp.readdir(resolvedPath);
-    return files.reduce<FileSources>((acc: FileSources, next: string) => {
+    return files.reduce((acc: FileSources, next: string) => {
       const nextPath = path.join(fileOrDir, next);
       return [...acc, ...collectLocalPathBehaviors(nextPath, depth + 1)];
     }, []);