diff --git a/utils/unambiguous.js b/utils/unambiguous.js
index 19fed08f6..e505be371 100644
--- a/utils/unambiguous.js
+++ b/utils/unambiguous.js
@@ -25,5 +25,5 @@ const unambiguousNodeType = /^(?:(?:Exp|Imp)ort.*Declaration|TSExportAssignment)
  * @return {Boolean}
  */
 exports.isModule = function isUnambiguousModule(ast) {
-  return ast.body.some(node => unambiguousNodeType.test(node.type))
+  return ast.body && ast.body.some(node => unambiguousNodeType.test(node.type))
 }