diff --git a/lib/tasks/listen.js b/lib/tasks/listen.js
index dc442722..a82a73e4 100644
--- a/lib/tasks/listen.js
+++ b/lib/tasks/listen.js
@@ -36,7 +36,8 @@ class TaskListen extends Task {
       this.metadata = {};
       for (const key in this.data.metadata) {
         if (this.data.metadata.hasOwnProperty(key)) {
-          this.metadata[key] = escapeString(this.data.metadata[key]);
+          const value = this.data.metadata[key];
+          this.metadata[key] = typeof value === 'string' ? escapeString(value) : value;
         }
       }
     }