diff --git a/matrix-sdk-android/src/rustCrypto/java/org/matrix/android/sdk/internal/crypto/OlmMachine.kt b/matrix-sdk-android/src/rustCrypto/java/org/matrix/android/sdk/internal/crypto/OlmMachine.kt
index 74d8724e79..fa0f5b7cb9 100644
--- a/matrix-sdk-android/src/rustCrypto/java/org/matrix/android/sdk/internal/crypto/OlmMachine.kt
+++ b/matrix-sdk-android/src/rustCrypto/java/org/matrix/android/sdk/internal/crypto/OlmMachine.kt
@@ -292,7 +292,11 @@ internal class OlmMachine @Inject constructor(
     }
 
     suspend fun receiveUnencryptedVerificationEvent(roomId: String, event: Event) = withContext(coroutineDispatchers.io) {
-        val adapter = moshi.adapter(Event::class.java)
+        val adapter = moshi
+                .newBuilder()
+                .add(CheckNumberType.JSON_ADAPTER_FACTORY)
+                .build()
+                .adapter(Event::class.java)
         val serializedEvent = adapter.toJson(event)
         inner.receiveUnencryptedVerificationEvent(serializedEvent, roomId)
     }