diff --git a/unified_planning/io/pddl_writer.py b/unified_planning/io/pddl_writer.py
index 2dbaa4569..a7f361e1a 100644
--- a/unified_planning/io/pddl_writer.py
+++ b/unified_planning/io/pddl_writer.py
@@ -611,9 +611,7 @@ def _write_domain(self, out: IO[str]):
                     for p in (c.simplify() for c in a.preconditions):
                         if not p.is_true():
                             if p.is_and():
-                                precond_str.extend(
-                                    map(converter.convert, p.args)
-                                )
+                                precond_str.extend(map(converter.convert, p.args))
                             else:
                                 precond_str.append(converter.convert(p))
                     preconditions_string = "\n                    ".join(precond_str)