diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3f40d245..221cf27b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,8 +8,9 @@
 
 ### Changed
 
-- **aiken-lang**: Fix underflow in error message reported by the validator arity. See [#1013](https://github.com/aiken-lang/aiken/issues/1013) @KtorZ.
+- **aiken-lang**: Fix underflow in error message reported by the validator arity. See [#1013](https://github.com/aiken-lang/aiken/issues/1013) @KtorZ
 - **aiken-lang**: Fix list-pattern needlessly formatting over multiple lines. @KtorZ
+- **aiken-lang**: Fix formatter on long alternative patterns spanning over multiple lines. @KtorZ
 
 ### Removed
 
diff --git a/crates/aiken-lang/src/format.rs b/crates/aiken-lang/src/format.rs
index 472f9925..7aadd6e6 100644
--- a/crates/aiken-lang/src/format.rs
+++ b/crates/aiken-lang/src/format.rs
@@ -1906,8 +1906,9 @@ impl<'comments> Formatter<'comments> {
         let space_before = self.pop_empty_lines(clause.location.start);
         let clause_doc = join(
             clause.patterns.iter().map(|p| self.pattern(p)),
-            " | ".to_doc(),
-        );
+            break_(" | ", " | "),
+        )
+        .group();
 
         if index == 0 {
             clause_doc
diff --git a/crates/aiken-lang/src/tests/format.rs b/crates/aiken-lang/src/tests/format.rs
index 0ea0f1c0..ee095e4d 100644
--- a/crates/aiken-lang/src/tests/format.rs
+++ b/crates/aiken-lang/src/tests/format.rs
@@ -1249,17 +1249,48 @@ fn format_validator_exhaustive_handlers_extra_non_default_fallback() {
 }
 
 #[test]
-fn list_pattern() {
+fn single_line_alternative_patterns() {
     assert_format!(
         r#"
         fn foo() {
-          when xs is {
-            [_] -> True
-            [1, 2] -> False
-            [_, x] -> {
-               let y = x
-               y == 42
+            when bar is {
+                a | b | c -> True
+                d | e -> {
+                    let x = e + d
+                    x > 10
+                }
+                _ -> False
             }
+        }
+        "#
+    );
+}
+
+#[test]
+fn multiline_alternative_patterns() {
+    assert_format!(
+        r#"
+        validator direct_proxy {
+          mint(_redeemer: Void, policy_id: PolicyId, self: Transaction) {
+            list.any(
+              self.certificates,
+              fn(certificate) {
+                when certificate is {
+                  RegisterDelegateRepresentative {
+                    delegate_representative: credential,
+                    ..
+                  } | UnregisterDelegateRepresentative {
+                    delegate_representative: credential,
+                    ..
+                  } | RegisterCredential { credential, .. } | UnregisterCredential {
+                    credential,
+                    ..
+                  } | RegisterAndDelegateCredential { credential, .. } ->
+                    credential == Script(policy_id)
+                  _ -> False
+                }
+              },
+            )
           }
         }
         "#
diff --git a/crates/aiken-lang/src/tests/snapshots/multiline_alternative_patterns.snap b/crates/aiken-lang/src/tests/snapshots/multiline_alternative_patterns.snap
new file mode 100644
index 00000000..ef36ad87
--- /dev/null
+++ b/crates/aiken-lang/src/tests/snapshots/multiline_alternative_patterns.snap
@@ -0,0 +1,32 @@
+---
+source: crates/aiken-lang/src/tests/format.rs
+description: "Code:\n\nvalidator direct_proxy {\n  mint(_redeemer: Void, policy_id: PolicyId, self: Transaction) {\n    list.any(\n      self.certificates,\n      fn(certificate) {\n        when certificate is {\n          RegisterDelegateRepresentative {\n            delegate_representative: credential,\n            ..\n          } | UnregisterDelegateRepresentative {\n            delegate_representative: credential,\n            ..\n          } | RegisterCredential { credential, .. } | UnregisterCredential {\n            credential,\n            ..\n          } | RegisterAndDelegateCredential { credential, .. } ->\n            credential == Script(policy_id)\n          _ -> False\n        }\n      },\n    )\n  }\n}\n"
+---
+validator direct_proxy {
+  mint(_redeemer: Void, policy_id: PolicyId, self: Transaction) {
+    list.any(
+      self.certificates,
+      fn(certificate) {
+        when certificate is {
+          RegisterDelegateRepresentative {
+            delegate_representative: credential,
+            ..
+          } | 
+          UnregisterDelegateRepresentative {
+            delegate_representative: credential,
+            ..
+          } | 
+          RegisterCredential { credential, .. } | 
+          UnregisterCredential { credential, .. } | 
+          RegisterAndDelegateCredential { credential, .. } ->
+            credential == Script(policy_id)
+          _ -> False
+        }
+      },
+    )
+  }
+
+  else(_) {
+    fail
+  }
+}
diff --git a/crates/aiken-lang/src/tests/snapshots/single_line_alternative_patterns.snap b/crates/aiken-lang/src/tests/snapshots/single_line_alternative_patterns.snap
new file mode 100644
index 00000000..d1d1dca5
--- /dev/null
+++ b/crates/aiken-lang/src/tests/snapshots/single_line_alternative_patterns.snap
@@ -0,0 +1,14 @@
+---
+source: crates/aiken-lang/src/tests/format.rs
+description: "Code:\n\nfn foo() {\n    when bar is {\n        a | b | c -> True\n        d | e -> {\n            let x = e + d\n            x > 10\n        }\n        _ -> False\n    }\n}\n"
+---
+fn foo() {
+  when bar is {
+    a | b | c -> True
+    d | e -> {
+      let x = e + d
+      x > 10
+    }
+    _ -> False
+  }
+}