diff --git a/tuf/api/metadata.py b/tuf/api/metadata.py
index 25f14fe772..58c7f0fd2d 100644
--- a/tuf/api/metadata.py
+++ b/tuf/api/metadata.py
@@ -722,7 +722,7 @@ def __init__(
         spec_version: str,
         expires: datetime,
         keys: Dict[str, Key],
-        roles: Dict[str, Role],
+        roles: Mapping[str, Role],
         consistent_snapshot: Optional[bool] = None,
         unrecognized_fields: Optional[Mapping[str, Any]] = None,
     ):