diff --git a/crates/aiken-lang/src/tests/check.rs b/crates/aiken-lang/src/tests/check.rs
index ff599dc8..b5265c1b 100644
--- a/crates/aiken-lang/src/tests/check.rs
+++ b/crates/aiken-lang/src/tests/check.rs
@@ -2131,6 +2131,40 @@ fn can_down_cast_to_data_always() {
     assert!(check(parse(source_code)).is_ok());
 }
 
+#[test]
+fn can_down_cast_to_data_on_fn_call() {
+    let source_code = r#"
+        pub type Foo { Foo }
+
+        pub fn serialise(data: Data) -> ByteArray {
+            ""
+        }
+
+        test foo() {
+            serialise(Foo) == ""
+        }
+    "#;
+
+    assert!(check(parse(source_code)).is_ok());
+}
+
+#[test]
+fn can_down_cast_to_data_on_pipe() {
+    let source_code = r#"
+        pub type Foo { Foo }
+
+        pub fn serialise(data: Data) -> ByteArray {
+            ""
+        }
+
+        test foo() {
+            (Foo |> serialise) == ""
+        }
+    "#;
+
+    assert!(check(parse(source_code)).is_ok());
+}
+
 #[test]
 fn correct_span_for_backpassing_args() {
     let source_code = r#"
diff --git a/crates/aiken-lang/src/tipo/environment.rs b/crates/aiken-lang/src/tipo/environment.rs
index 430b6754..49f46a52 100644
--- a/crates/aiken-lang/src/tipo/environment.rs
+++ b/crates/aiken-lang/src/tipo/environment.rs
@@ -1431,7 +1431,7 @@ impl<'a> Environment<'a> {
                     lhs,
                     Type::with_alias(tipo.clone(), alias.clone()),
                     location,
-                    false,
+                    allow_cast,
                 );
             }
         }
@@ -1470,7 +1470,7 @@ impl<'a> Environment<'a> {
                     Ok(())
                 }
 
-                Action::Unify(t) => self.unify(t, rhs, location, false),
+                Action::Unify(t) => self.unify(t, rhs, location, allow_cast),
 
                 Action::CouldNotUnify => Err(Error::CouldNotUnify {
                     location,
@@ -1550,7 +1550,7 @@ impl<'a> Environment<'a> {
                 },
             ) if args1.len() == args2.len() => {
                 for (a, b) in args1.iter().zip(args2) {
-                    self.unify(a.clone(), b.clone(), location, false)
+                    self.unify(a.clone(), b.clone(), location, allow_cast)
                         .map_err(|_| Error::CouldNotUnify {
                             location,
                             expected: lhs.clone(),