diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/create/CreateRoomParams.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/create/CreateRoomParams.kt
index d9fb8803b4..77c4fcf1e2 100644
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/create/CreateRoomParams.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/create/CreateRoomParams.kt
@@ -210,11 +210,7 @@ class CreateRoomParams {
      * @return the first invited user id
      */
     fun getFirstInvitedUserId(): String? {
-        if (getInviteCount() > 0) {
-            return invitedUserIds?.firstOrNull()
-        }
-
-        return invite3pids?.firstOrNull()?.address
+        return invitedUserIds?.firstOrNull() ?: invite3pids?.firstOrNull()?.address
     }
 
     /**
diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/algorithms/olm/MXOlmDecryption.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/algorithms/olm/MXOlmDecryption.kt
index 08107f6aa7..2714784c23 100644
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/algorithms/olm/MXOlmDecryption.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/algorithms/olm/MXOlmDecryption.kt
@@ -176,7 +176,7 @@ internal class MXOlmDecryption(
             sessionIds = ArrayList(sessionIdsSet)
         }
 
-        val messageBody = message["body"] as String?
+        val messageBody = message["body"] as? String
         var messageType: Int? = null
 
         val typeAsVoid = message["type"]
diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/keysbackup/KeysBackup.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/keysbackup/KeysBackup.kt
index 1d4423998c..4dc3c634f1 100644
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/keysbackup/KeysBackup.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/keysbackup/KeysBackup.kt
@@ -45,7 +45,6 @@ import im.vector.matrix.android.internal.crypto.keysbackup.tasks.*
 import im.vector.matrix.android.internal.crypto.keysbackup.util.computeRecoveryKey
 import im.vector.matrix.android.internal.crypto.keysbackup.util.extractCurveKeyFromRecoveryKey
 import im.vector.matrix.android.internal.crypto.model.ImportRoomKeysResult
-import im.vector.matrix.android.internal.crypto.model.MXDeviceInfo
 import im.vector.matrix.android.internal.crypto.model.OlmInboundGroupSessionWrapper
 import im.vector.matrix.android.internal.crypto.store.IMXCryptoStore
 import im.vector.matrix.android.internal.crypto.store.db.model.KeysBackupDataEntity
@@ -389,7 +388,7 @@ internal class KeysBackup @Inject constructor(
         }
 
         val mySigs = authData.signatures?.get(myUserId)
-        if (mySigs == null || mySigs.isEmpty()) {
+        if (mySigs.isNullOrEmpty()) {
             Timber.v("getKeysBackupTrust: Ignoring key backup because it lacks any signatures from this user")
             return keysBackupVersionTrust
         }
@@ -403,18 +402,20 @@ internal class KeysBackup @Inject constructor(
             }
 
             if (deviceId != null) {
-                var device = cryptoStore.getUserDevice(deviceId, myUserId)
-
+                val device = cryptoStore.getUserDevice(deviceId, myUserId)
                 var isSignatureValid = false
 
                 if (device == null) {
                     Timber.v("getKeysBackupTrust: Signature from unknown device $deviceId")
                 } else {
-                    try {
-                        olmDevice.verifySignature(device.fingerprint()!!, authData.signalableJSONDictionary(), mySigs[keyId] as String)
-                        isSignatureValid = true
-                    } catch (e: OlmException) {
-                        Timber.v("getKeysBackupTrust: Bad signature from device " + device.deviceId + " " + e.localizedMessage)
+                    val fingerprint = device.fingerprint()
+                    if (fingerprint != null) {
+                        try {
+                            olmDevice.verifySignature(fingerprint, authData.signalableJSONDictionary(), mySigs[keyId] as String)
+                            isSignatureValid = true
+                        } catch (e: OlmException) {
+                            Timber.v("getKeysBackupTrust: Bad signature from device " + device.deviceId + " " + e.localizedMessage)
+                        }
                     }
 
                     if (isSignatureValid && device.isVerified) {
diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/model/MXDeviceInfo.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/model/MXDeviceInfo.kt
index cee17f2e00..a458cdfe03 100755
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/model/MXDeviceInfo.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/crypto/model/MXDeviceInfo.kt
@@ -124,7 +124,7 @@ data class MXDeviceInfo(
      * @return the display name
      */
     fun displayName(): String? {
-        return unsigned?.get("device_display_name") as String?
+        return unsigned?.get("device_display_name") as? String
     }
 
     /**