diff --git a/py/stencila/schema/interpreter.py b/py/stencila/schema/interpreter.py
index 9e79879f..8f833da7 100644
--- a/py/stencila/schema/interpreter.py
+++ b/py/stencila/schema/interpreter.py
@@ -353,6 +353,12 @@ def parse_function_def(self, statement: ast.FunctionDef) -> None:
 
             f.parameters.append(p)
 
+        if statement.args.vararg:
+            f.parameters.append(Parameter(statement.args.vararg.arg, required=False, repeats=True))
+
+        if statement.args.kwarg:
+            f.parameters.append(Parameter(statement.args.kwarg.arg, required=False, extends=True))
+
         self.seen_vars.append(f.name)
         self.declares.append(f)