diff --git a/crates/matrix-sdk-base/Cargo.toml b/crates/matrix-sdk-base/Cargo.toml
index 4243806ff55..7373797a9e3 100644
--- a/crates/matrix-sdk-base/Cargo.toml
+++ b/crates/matrix-sdk-base/Cargo.toml
@@ -27,6 +27,11 @@ experimental-sliding-sync = [
 ]
 uniffi = ["dep:uniffi", "matrix-sdk-crypto?/uniffi", "matrix-sdk-common/uniffi"]
 
+# Private feature, see
+# https://github.com/matrix-org/matrix-rust-sdk/pull/3749#issuecomment-2312939823 for the gory
+# details.
+test-send-sync = []
+
 # "message-ids" feature doesn't do anything and is deprecated.
 message-ids = []
 
diff --git a/crates/matrix-sdk-base/src/rooms/normal.rs b/crates/matrix-sdk-base/src/rooms/normal.rs
index 7028e88d01d..0d08370cd8c 100644
--- a/crates/matrix-sdk-base/src/rooms/normal.rs
+++ b/crates/matrix-sdk-base/src/rooms/normal.rs
@@ -992,6 +992,23 @@ impl Room {
     }
 }
 
+// See https://github.com/matrix-org/matrix-rust-sdk/pull/3749#issuecomment-2312939823.
+#[cfg(not(feature = "test-send-sync"))]
+unsafe impl Send for Room {}
+
+// See https://github.com/matrix-org/matrix-rust-sdk/pull/3749#issuecomment-2312939823.
+#[cfg(not(feature = "test-send-sync"))]
+unsafe impl Sync for Room {}
+
+#[cfg(feature = "test-send-sync")]
+#[test]
+// See https://github.com/matrix-org/matrix-rust-sdk/pull/3749#issuecomment-2312939823.
+fn test_send_sync_for_room() {
+    fn assert_send_sync<T: Send + Sync>() {}
+
+    assert_send_sync::<Room>();
+}
+
 /// The underlying pure data structure for joined and left rooms.
 ///
 /// Holds all the info needed to persist a room into the state store.
diff --git a/xtask/src/ci.rs b/xtask/src/ci.rs
index 56ac0f9a679..4507baf44c1 100644
--- a/xtask/src/ci.rs
+++ b/xtask/src/ci.rs
@@ -293,7 +293,7 @@ fn run_wasm_checks(cmd: Option<WasmFeatureSet>) -> Result<()> {
             WasmFeatureSet::MatrixSdkNoDefault,
             "-p matrix-sdk --no-default-features --features js,rustls-tls",
         ),
-        (WasmFeatureSet::MatrixSdkBase, "-p matrix-sdk-base --features js"),
+        (WasmFeatureSet::MatrixSdkBase, "-p matrix-sdk-base --features js,test-send-sync"),
         (WasmFeatureSet::MatrixSdkCommon, "-p matrix-sdk-common --features js"),
         (
             WasmFeatureSet::MatrixSdkIndexeddbStoresNoCrypto,