diff --git a/examples/acceptance_tests/035/aiken.lock b/examples/acceptance_tests/035/aiken.lock
new file mode 100644
index 00000000..3a78b1e7
--- /dev/null
+++ b/examples/acceptance_tests/035/aiken.lock
@@ -0,0 +1,5 @@
+# This file was generated by Aiken
+# You typically do not need to edit this file
+
+requirements = []
+packages = []
diff --git a/examples/acceptance_tests/035/aiken.toml b/examples/acceptance_tests/035/aiken.toml
new file mode 100644
index 00000000..a9c17672
--- /dev/null
+++ b/examples/acceptance_tests/035/aiken.toml
@@ -0,0 +1,2 @@
+name = "aiken-lang/acceptance_test_035"
+version = "0.0.0"
diff --git a/examples/acceptance_tests/035/lib/aiken/dict.ak b/examples/acceptance_tests/035/lib/aiken/dict.ak
new file mode 100644
index 00000000..f34d83bb
--- /dev/null
+++ b/examples/acceptance_tests/035/lib/aiken/dict.ak
@@ -0,0 +1,60 @@
+/// An opaque `Dict`. The type is opaque because the module maintains some
+/// invariant, namely: there's only one occurence of a given key in the dictionnary.
+pub opaque type Dict<key, value> {
+  inner: List<#(ByteArray, value)>,
+}
+
+/// Create a new map
+pub fn new() -> Dict<key, value> {
+  Dict { inner: [] }
+}
+
+pub fn insert(
+  self: Dict<ByteArray, value>,
+  key k: ByteArray,
+  value v: value,
+) -> Dict<key, value> {
+  Dict {
+  inner: do_insert_with(self.inner, k, v, fn(_, left, _right) { Some(left) })}
+  
+}
+
+pub fn union_with(
+  left: Dict<key, value>,
+  right: Dict<key, value>,
+  with: fn(ByteArray, value, value) -> Option<value>,
+) -> Dict<key, value> {
+  Dict { inner: do_union_with(left.inner, right.inner, with) }
+}
+
+fn do_union_with(
+  left: List<#(ByteArray, value)>,
+  right: List<#(ByteArray, value)>,
+  with: fn(ByteArray, value, value) -> Option<value>,
+) -> List<#(ByteArray, value)> {
+  when left is {
+    [] -> right
+    [#(k, v), ..rest] ->
+      do_union_with(rest, do_insert_with(right, k, v, with), with)
+  }
+}
+
+fn do_insert_with(
+  self: List<#(ByteArray, value)>,
+  key k: ByteArray,
+  value v: value,
+  with: fn(ByteArray, value, value) -> Option<value>,
+) -> List<#(ByteArray, value)> {
+  when self is {
+    [] -> [#(k, v)]
+    [#(k2, v2), ..rest] ->
+      if k == k2 {
+        when with(k, v, v2) is {
+          Some(combined) -> [#(k, combined), ..rest]
+          None -> rest
+        }
+      } else {
+        [#(k2, v2), ..do_insert_with(rest, k, v, with)]
+      }
+  }
+}
diff --git a/examples/acceptance_tests/035/lib/tests.ak b/examples/acceptance_tests/035/lib/tests.ak
new file mode 100644
index 00000000..597c6968
--- /dev/null
+++ b/examples/acceptance_tests/035/lib/tests.ak
@@ -0,0 +1,55 @@
+use aiken/dict.{Dict}
+
+pub type PolicyId =
+  ByteArray
+
+pub type AssetName =
+  ByteArray
+
+pub type Value =
+  Dict<PolicyId, Dict<AssetName, Int>>
+
+pub fn from_asset(
+  policy_id: PolicyId,
+  asset_name: AssetName,
+  quantity: Int,
+) -> Value {
+  let asset =
+    dict.new()
+    |> dict.insert(asset_name, quantity)
+  dict.new()
+  |> dict.insert(policy_id, asset)
+}
+
+pub fn from_lovelace(quantity: Int) -> Value {
+  from_asset(#[], #[], quantity)
+}
+
+pub fn add(left v0: Value, right v1: Value) -> Value {
+  dict.union_with(
+    v0,
+    v1,
+    fn(_, a0, a1) {
+      Some(
+      dict.union_with(
+        a0,
+        a1,
+        fn(_, q0, q1) {
+          let q = q0 + q1
+          if q == 0 {
+            None
+          } else {
+            Some(q)
+          }
+        },
+      ))
+      
+    },
+  )
+}
+
+test add_1() {
+  let v1 = from_lovelace(1)
+  let v2 = from_lovelace(-1)
+  add(v1, v2) == dict.new()
+}