diff --git a/src/logging/diagnostic-session-context.ts b/src/logging/diagnostic-session-context.ts
index 4194be4619f..5f450b62571 100644
--- a/src/logging/diagnostic-session-context.ts
+++ b/src/logging/diagnostic-session-context.ts
@@ -106,7 +106,7 @@ export function readLastAssistantFromSessionFile(filePath: string | undefined):
     return undefined;
   }
   const tail = readTailText(filePath);
-  if (!tail.text) {
+  if (!tail?.text) {
     return undefined;
   }
   const lines = tail.text.split(/\r?\n/).filter(Boolean);