diff --git a/examples/acceptance_tests/020/aiken.toml b/examples/acceptance_tests/020/aiken.toml
new file mode 100644
index 00000000..10ee4051
--- /dev/null
+++ b/examples/acceptance_tests/020/aiken.toml
@@ -0,0 +1,2 @@
+name = "acceptance_test_020"
+version = "0.0.0"
diff --git a/examples/acceptance_tests/020/lib/test.ak b/examples/acceptance_tests/020/lib/test.ak
new file mode 100644
index 00000000..a199733d
--- /dev/null
+++ b/examples/acceptance_tests/020/lib/test.ak
@@ -0,0 +1,10 @@
+pub fn map(opt: Option<a>, f: fn(a) -> result) -> Option<result> {
+  when opt is {
+    None -> None
+    Some(a) -> Some(f(a))
+  }
+}
+
+test map_2() {
+  map(Some(14), fn(n) { n + 1 }) == Some(15)
+}