diff --git a/test/function/top-level-side-effects-are-preserved/_config.js b/test/function/top-level-side-effects-are-preserved/_config.js
new file mode 100644
index 0000000..b121b33
--- /dev/null
+++ b/test/function/top-level-side-effects-are-preserved/_config.js
@@ -0,0 +1,3 @@
+module.exports = {
+  description: 'top level side effects are preserved'
+};
diff --git a/test/function/top-level-side-effects-are-preserved/asap.js b/test/function/top-level-side-effects-are-preserved/asap.js
new file mode 100644
index 0000000..6b43f3a
--- /dev/null
+++ b/test/function/top-level-side-effects-are-preserved/asap.js
@@ -0,0 +1 @@
+export default function asap() {}
diff --git a/test/function/top-level-side-effects-are-preserved/config.js b/test/function/top-level-side-effects-are-preserved/config.js
new file mode 100644
index 0000000..c4470d2
--- /dev/null
+++ b/test/function/top-level-side-effects-are-preserved/config.js
@@ -0,0 +1 @@
+export const config = {};
diff --git a/test/function/top-level-side-effects-are-preserved/defer.js b/test/function/top-level-side-effects-are-preserved/defer.js
new file mode 100644
index 0000000..2ab1d6d
--- /dev/null
+++ b/test/function/top-level-side-effects-are-preserved/defer.js
@@ -0,0 +1,5 @@
+import { config } from './config';
+
+export default function defer() {
+  config.async();
+}
diff --git a/test/function/top-level-side-effects-are-preserved/main.js b/test/function/top-level-side-effects-are-preserved/main.js
new file mode 100644
index 0000000..d844cc0
--- /dev/null
+++ b/test/function/top-level-side-effects-are-preserved/main.js
@@ -0,0 +1,3 @@
+import { defer } from './rsvp';
+
+defer();
diff --git a/test/function/top-level-side-effects-are-preserved/rsvp.js b/test/function/top-level-side-effects-are-preserved/rsvp.js
new file mode 100644
index 0000000..d3bcb42
--- /dev/null
+++ b/test/function/top-level-side-effects-are-preserved/rsvp.js
@@ -0,0 +1,7 @@
+import { config } from './config';
+import asap from './asap';
+import defer from './defer';
+
+config.async = asap;
+
+export { defer };