diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index c35301207ae4..e00cb7096ccd 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -100,9 +100,6 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
         # MSC3773: Thread notifications
         self.msc3773_enabled: bool = experimental.get("msc3773_enabled", False)
 
-        # MSC3715: dir param on /relations.
-        self.msc3715_enabled: bool = experimental.get("msc3715_enabled", False)
-
         # MSC3848: Introduce errcodes for specific event sending failures
         self.msc3848_enabled: bool = experimental.get("msc3848_enabled", False)
 
diff --git a/synapse/rest/client/relations.py b/synapse/rest/client/relations.py
index 7a25de5c8596..747437fed44c 100644
--- a/synapse/rest/client/relations.py
+++ b/synapse/rest/client/relations.py
@@ -43,7 +43,6 @@ def __init__(self, hs: "HomeServer"):
         self.auth = hs.get_auth()
         self.store = hs.get_datastores().main
         self._relations_handler = hs.get_relations_handler()
-        self._msc3715_enabled = hs.config.experimental.msc3715_enabled
 
     async def on_GET(
         self,
@@ -60,17 +59,7 @@ async def on_GET(
         #
         # TODO Use PaginationConfig.from_request when the unstable parameter is
         #      no longer needed.
-        direction = parse_string(request, "dir", allowed_values=["f", "b"])
-        if direction is None:
-            if self._msc3715_enabled:
-                direction = parse_string(
-                    request,
-                    "org.matrix.msc3715.dir",
-                    default="b",
-                    allowed_values=["f", "b"],
-                )
-            else:
-                direction = "b"
+        direction = parse_string(request, "dir", default="b", allowed_values=["f", "b"])
         from_token_str = parse_string(request, "from")
         to_token_str = parse_string(request, "to")