diff --git a/server/express/user.ts b/server/express/user.ts
index 33e140bfe..0fad0b031 100644
--- a/server/express/user.ts
+++ b/server/express/user.ts
@@ -825,7 +825,7 @@ const isValidAvatarSource = (source: string | null): boolean => {
         return true;
     }
 
-    if (process.env.CLOUDFRONT && source.startsWith(process.env.CLOUDFRONT + '/')) {
+    if (process.env.CLOUDFRONT && source.startsWith(`${process.env.CLOUDFRONT}/`)) {
         return true;
     }