diff --git a/packages/core/src/analyzer/AnalyzerManager.ts b/packages/core/src/analyzer/AnalyzerManager.ts
index 86432130..5ca501a1 100644
--- a/packages/core/src/analyzer/AnalyzerManager.ts
+++ b/packages/core/src/analyzer/AnalyzerManager.ts
@@ -298,6 +298,8 @@ export class AnalyzerManager {
 
   async getUrl(rule: string, host: string): Promise<string> {
     let url = await this.getString(rule)
+    if (typeof url !== 'string')
+      return url
 
     if (url.startsWith('//')) {
       if (host.startsWith('https'))