diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/rendezvous/channels/ECDHRendezvousChannel.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/rendezvous/channels/ECDHRendezvousChannel.kt
index 489d20e588..ca7083b297 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/rendezvous/channels/ECDHRendezvousChannel.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/rendezvous/channels/ECDHRendezvousChannel.kt
@@ -90,43 +90,45 @@ class ECDHRendezvousChannel(override var transport: RendezvousTransport, theirPu
     }
 
     override suspend fun connect(): String {
-        if (olmSAS == null) {
-            throw RuntimeException("Channel closed")
-        }
-        val isInitiator = theirPublicKey == null
+        olmSAS ?.let { olmSAS ->
+            val isInitiator = theirPublicKey == null
 
-        if (isInitiator) {
-            Timber.tag(TAG).i("Waiting for other device to send their public key")
-            val res = this.receiveAsPayload() ?: throw RuntimeException("No reply from other device")
+            if (isInitiator) {
+                Timber.tag(TAG).i("Waiting for other device to send their public key")
+                val res = this.receiveAsPayload() ?: throw RuntimeException("No reply from other device")
 
-            if (res.key == null) {
-                throw RendezvousError(
-                        "Unsupported algorithm: ${res.algorithm}",
-                        RendezvousFailureReason.UnsupportedAlgorithm,
+                if (res.key == null) {
+                    throw RendezvousError(
+                            "Unsupported algorithm: ${res.algorithm}",
+                            RendezvousFailureReason.UnsupportedAlgorithm,
+                    )
+                }
+                theirPublicKey = Base64.decode(res.key, Base64.NO_WRAP)
+            } else {
+                // send our public key unencrypted
+                Timber.tag(TAG).i("Sending public key")
+                send(
+                        ECDHPayload(
+                                algorithm = SecureRendezvousChannelAlgorithm.ECDH_V1,
+                                key = Base64.encodeToString(ourPublicKey, Base64.NO_WRAP)
+                        )
                 )
             }
-            theirPublicKey = Base64.decode(res.key, Base64.NO_WRAP)
-        } else {
-            // send our public key unencrypted
-            Timber.tag(TAG).i("Sending public key")
-            send(
-                    ECDHPayload(
-                    algorithm = SecureRendezvousChannelAlgorithm.ECDH_V1,
-                    key = Base64.encodeToString(ourPublicKey, Base64.NO_WRAP)
-            )
-            )
-        }
 
-        olmSAS!!.setTheirPublicKey(Base64.encodeToString(theirPublicKey, Base64.NO_WRAP))
+            synchronized(olmSAS) {
+                olmSAS.setTheirPublicKey(Base64.encodeToString(theirPublicKey, Base64.NO_WRAP))
+                olmSAS.setTheirPublicKey(Base64.encodeToString(theirPublicKey, Base64.NO_WRAP))
 
-        val initiatorKey = Base64.encodeToString(if (isInitiator) ourPublicKey else theirPublicKey, Base64.NO_WRAP)
-        val recipientKey = Base64.encodeToString(if (isInitiator) theirPublicKey else ourPublicKey, Base64.NO_WRAP)
-        val aesInfo = "${SecureRendezvousChannelAlgorithm.ECDH_V1.value}|$initiatorKey|$recipientKey"
+                val initiatorKey = Base64.encodeToString(if (isInitiator) ourPublicKey else theirPublicKey, Base64.NO_WRAP)
+                val recipientKey = Base64.encodeToString(if (isInitiator) theirPublicKey else ourPublicKey, Base64.NO_WRAP)
+                val aesInfo = "${SecureRendezvousChannelAlgorithm.ECDH_V1.value}|$initiatorKey|$recipientKey"
 
-        aesKey = olmSAS!!.generateShortCode(aesInfo, 32)
+                aesKey = olmSAS.generateShortCode(aesInfo, 32)
 
-        val rawChecksum = olmSAS!!.generateShortCode(aesInfo, 5)
-        return getDecimalCodeRepresentation(rawChecksum)
+                val rawChecksum = olmSAS.generateShortCode(aesInfo, 5)
+                return getDecimalCodeRepresentation(rawChecksum)
+            }
+        } ?: throw RuntimeException("Channel closed")
     }
 
     private suspend fun send(payload: ECDHPayload) {
@@ -174,8 +176,13 @@ class ECDHRendezvousChannel(override var transport: RendezvousTransport, theirPu
     }
 
     override suspend fun close() {
-        olmSAS?.releaseSas()
-        olmSAS = null
+        olmSAS ?.let {
+            synchronized(it) {
+                // this does a double release check already so we don't re-check ourselves
+                it.releaseSas()
+                olmSAS = null
+            }
+        }
     }
 
     private fun encrypt(plainText: ByteArray): ECDHPayload {