diff --git a/lib/rules/hashbang.js b/lib/rules/hashbang.js
index 5199e5b5..3b9a0fa1 100644
--- a/lib/rules/hashbang.js
+++ b/lib/rules/hashbang.js
@@ -50,7 +50,7 @@ function isNodeShebang(shebang, executableName) {
  * @returns {string}
  */
 function getExpectedExecutableName(context) {
-    const extension = path.extname(context.filename)
+    const extension = path.extname(context.filename ?? context.getFilename())
     /** @type {{ executableMap: Record<string, string> }} */
     const { executableMap = {} } = context.options?.[0] ?? {}