diff --git a/ee/tabby-ui/lib/utils/index.ts b/ee/tabby-ui/lib/utils/index.ts
index 938068fe15a8..febf45bf59de 100644
--- a/ee/tabby-ui/lib/utils/index.ts
+++ b/ee/tabby-ui/lib/utils/index.ts
@@ -112,11 +112,11 @@ export function getRangeFromAttachmentCode(code: {
   startLine?: Maybe<number>
   content: string
 }): LineRange | undefined {
-  if (!code?.startLine) return undefined
+  if (!code?.startLine || typeof code.startLine !== 'number') return undefined
 
   const start = code.startLine
   const lineCount = code.content.split('\n').length
-  const end = typeof start === 'number' ? start + lineCount - 1 : 0
+  const end = start + lineCount - 1
 
   return {
     start,