diff --git a/harness.py b/harness.py
index 8d7abb2..56470ef 100644
--- a/harness.py
+++ b/harness.py
@@ -506,7 +506,8 @@ class Harness:
         lines.extend(node.format_lines(self.source))
 
     def format_document(self, lines: list[str], doc: wadler.Document, indent: int = 0):
-        def append(x: str):
+        def append(x: str, i: int = 0):
+            i += indent
             lines.append(("    " * indent) + x)
 
         match doc:
@@ -540,6 +541,14 @@ class Harness:
                 self.format_document(lines, doc.left, indent)
                 self.format_document(lines, doc.right, indent)
 
+            case wadler.Marker():
+                append("Marker")
+                append("metadata", 1)
+                for k, v in doc.meta.items():
+                    append(f"{k}={v}", 2)
+                append("child", 1)
+                self.format_document(lines, doc.child, indent + 2)
+
             case None:
                 pass
 
diff --git a/parser/wadler.py b/parser/wadler.py
index 75bedda..fe73d99 100644
--- a/parser/wadler.py
+++ b/parser/wadler.py
@@ -54,6 +54,12 @@ class Group:
     child: "Document"
 
 
+@dataclasses.dataclass(frozen=True)
+class Marker:
+    child: "Document"
+    meta: dict
+
+
 @dataclasses.dataclass
 class Lazy:
     value: typing.Callable[[], "Document"] | "Document"
@@ -68,7 +74,7 @@ class Lazy:
         return Lazy(lambda: printer.convert_tree_to_document(tree))
 
 
-Document = None | Text | Literal | NewLine | ForceBreak | Cons | Indent | Group | Lazy
+Document = None | Text | Literal | NewLine | ForceBreak | Cons | Indent | Group | Marker | Lazy
 
 
 class DocumentLayout:
@@ -162,6 +168,9 @@ def layout_document(doc: Document, width: int) -> DocumentLayout:
                     # well.)
                     stack.append(chunk.with_document(child))
 
+                case Marker():
+                    stack.append(chunk.with_document(chunk.doc.child))
+
                 case _:
                     typing.assert_never(chunk.doc)
 
@@ -216,6 +225,9 @@ def layout_document(doc: Document, width: int) -> DocumentLayout:
                 else:
                     chunks.append(Chunk(doc=child, indent=chunk.indent, flat=False))
 
+            case Marker():
+                chunks.append(chunk.with_document(chunk.doc.child))
+
             case _:
                 typing.assert_never(chunk)