diff --git a/packages/core/src/tools/grep.test.ts b/packages/core/src/tools/grep.test.ts
index 5b0ca9442e..c2609459e2 100644
--- a/packages/core/src/tools/grep.test.ts
+++ b/packages/core/src/tools/grep.test.ts
@@ -330,7 +330,7 @@ describe('GrepTool', () => {
 
       // Count occurrences of match lines in the output
       // Matches lines start with L<number>:
-      const matches = result.llmContent.match(/^L\d+:.*world/gm);
+      const matches = (result.llmContent as string).match(/^L\d+:.*world/gm);
       expect(matches?.length).toBe(2);
     }, 30000);
   });