diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index 43db5fcdd9..37dca57f95 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -81,3 +81,6 @@ class ExperimentalConfig(Config):
 
         # MSC2654: Unread counts
         self.msc2654_enabled: bool = experimental.get("msc2654_enabled", False)
+
+        # MSC3759: Leave event metadata for deactivated users
+        self.msc3759_enabled: bool = experimental.get("msc3759_enabled", False)