diff --git a/package.json b/package.json
index d67dbb7..ffc861a 100644
--- a/package.json
+++ b/package.json
@@ -12,7 +12,7 @@
   },
   "homepage": "https://github.com/thlorenz/rename-function-calls",
   "dependencies": {
-    "detective": "~3.1.0"
+    "detective": "4.x.x"
   },
   "devDependencies": {
     "tap": "~0.4.3"
diff --git a/test/fixtures/async-function.js b/test/fixtures/async-function.js
new file mode 100644
index 0000000..6e638f7
--- /dev/null
+++ b/test/fixtures/async-function.js
@@ -0,0 +1,23 @@
+// { "from": "xxx", "to": "x" }
+'use strict';
+
+function x() { }
+function y() { }
+function z() { }
+
+var go = module.exports = async function () {
+  xxx();  
+  y();
+  z();
+
+  function nested() {
+    return xxx();
+    function oneMoreLevel () {
+      xxx(); z(); xxx();
+    }
+  }
+
+  function nestedExpression() {
+    return 1 + xxx();
+  }
+};
diff --git a/test/fixtures/async-function.renamed.js b/test/fixtures/async-function.renamed.js
new file mode 100644
index 0000000..af65274
--- /dev/null
+++ b/test/fixtures/async-function.renamed.js
@@ -0,0 +1,22 @@
+'use strict';
+
+function x() { }
+function y() { }
+function z() { }
+
+var go = module.exports = async function () {
+  x();  
+  y();
+  z();
+
+  function nested() {
+    return x();
+    function oneMoreLevel () {
+      x(); z(); x();
+    }
+  }
+
+  function nestedExpression() {
+    return 1 + x();
+  }
+};