diff --git a/backend/src/templateFormatter.ts b/backend/src/templateFormatter.ts
index 4f9c1f81..84e24db5 100644
--- a/backend/src/templateFormatter.ts
+++ b/backend/src/templateFormatter.ts
@@ -389,7 +389,7 @@ const baseValues = {
     return baseValues.upperFirst(arg);
   },
   strlen(arg) {
-    if (typeof arg !== "string") return arg;
+    if (typeof arg !== "string") return 0;
     return arg.length;
   },
   rand(from, to, seed = null) {