diff --git a/crates/ruma-common/Cargo.toml b/crates/ruma-common/Cargo.toml
index 5e0c9031..910bb3f3 100644
--- a/crates/ruma-common/Cargo.toml
+++ b/crates/ruma-common/Cargo.toml
@@ -43,6 +43,7 @@ unstable-msc3551 = ["unstable-msc1767"]
 unstable-msc3552 = ["unstable-msc3551"]
 unstable-msc3553 = ["unstable-msc3552"]
 unstable-msc3554 = ["unstable-msc1767"]
+unstable-msc3700 = []
 
 [dependencies]
 base64 = "0.13.0"
diff --git a/crates/ruma-common/src/events/room/encrypted.rs b/crates/ruma-common/src/events/room/encrypted.rs
index 76385103..b3036048 100644
--- a/crates/ruma-common/src/events/room/encrypted.rs
+++ b/crates/ruma-common/src/events/room/encrypted.rs
@@ -264,9 +264,11 @@ pub struct MegolmV1AesSha2Content {
     pub ciphertext: String,
 
     /// The Curve25519 key of the sender.
+    #[cfg_attr(feature = "unstable-msc3700", deprecated = "as of Matrix v1.3")]
     pub sender_key: String,
 
     /// The ID of the sending device.
+    #[cfg_attr(feature = "unstable-msc3700", deprecated = "as of Matrix v1.3")]
     pub device_id: OwnedDeviceId,
 
     /// The ID of the session used to encrypt the message.
diff --git a/crates/ruma-common/src/events/room_key_request.rs b/crates/ruma-common/src/events/room_key_request.rs
index 20c41044..e21c251c 100644
--- a/crates/ruma-common/src/events/room_key_request.rs
+++ b/crates/ruma-common/src/events/room_key_request.rs
@@ -81,6 +81,7 @@ pub struct RequestedKeyInfo {
     pub room_id: OwnedRoomId,
 
     /// The Curve25519 key of the device which initiated the session originally.
+    #[cfg_attr(feature = "unstable-msc3700", deprecated = "as of Matrix v1.3")]
     pub sender_key: String,
 
     /// The ID of the session that the key is for.