diff --git a/app/src/main/java/com/tangem/data/Blockchain.java b/app/src/main/java/com/tangem/data/Blockchain.java
index 370a986e45..402348982e 100644
--- a/app/src/main/java/com/tangem/data/Blockchain.java
+++ b/app/src/main/java/com/tangem/data/Blockchain.java
@@ -6,7 +6,7 @@ import com.tangem.tangem_sdk.R;
  * Created by dvol on 06.08.2017.
  */
 public enum Blockchain {
-    Unknown("", "", 1.0, R.drawable.ic_logo_unknown, ""),
+    Unknown("", "", 1.0, R.drawable.ic_logo_unknown, "Unknown"),
     Bitcoin("BTC", "BTC", 100000000.0, R.drawable.ic_logo_bitcoin, "Bitcoin"),
     BitcoinTestNet("BTC/test", "BTC", 100000000.0, R.drawable.ic_logo_bitcoin_testnet, "Bitcoin Testnet"),
     BitcoinDual("BTC/dual", "BTC", 100000000.0, R.drawable.ic_logo_bitcoin, "Bitcoin"),
@@ -68,7 +68,7 @@ public enum Blockchain {
         for (Blockchain blockchain : values()) {
             if (blockchain.getID().equals(id)) return blockchain;
         }
-        return null;
+        return Blockchain.Unknown;
     }
 
     public static Blockchain fromCurrency(String currency) {
diff --git a/app/src/main/java/com/tangem/ui/activity/MainActivity.kt b/app/src/main/java/com/tangem/ui/activity/MainActivity.kt
index c5bdb69201..8c6f685715 100644
--- a/app/src/main/java/com/tangem/ui/activity/MainActivity.kt
+++ b/app/src/main/java/com/tangem/ui/activity/MainActivity.kt
@@ -8,6 +8,7 @@ import android.nfc.Tag
 import android.os.Bundle
 import android.util.Log
 import androidx.appcompat.app.AppCompatActivity
+import androidx.fragment.app.Fragment
 import androidx.lifecycle.ViewModelProviders
 import androidx.navigation.findNavController
 import com.scottyab.rootbeer.RootBeer
@@ -16,6 +17,7 @@ import com.tangem.di.ToastHelper
 import com.tangem.tangem_sdk.android.nfc.NfcLifecycleObserver
 import com.tangem.tangem_sdk.android.reader.NfcManager
 import com.tangem.ui.dialog.RootFoundDialog
+import com.tangem.ui.fragment.MainFragment
 import com.tangem.wallet.BuildConfig
 import com.tangem.wallet.R
 import javax.inject.Inject
@@ -44,6 +46,8 @@ class MainActivity : AppCompatActivity(), NfcAdapter.ReaderCallback {
     }
 
     private fun navigateSafelyToMainFragment() {
+        if (getActiveFragment() is MainFragment) return
+
         try {
             findNavController(R.id.nav_host_fragment).popBackStack()
         } catch (e: IllegalArgumentException) {
@@ -73,8 +77,7 @@ class MainActivity : AppCompatActivity(), NfcAdapter.ReaderCallback {
     }
 
     override fun onTagDiscovered(tag: Tag) {
-        val activeFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment)
-                ?.childFragmentManager?.primaryNavigationFragment
+        val activeFragment = getActiveFragment()
         if (activeFragment is NfcAdapter.ReaderCallback) {
             activeFragment.onTagDiscovered(tag)
         } else {
@@ -82,4 +85,8 @@ class MainActivity : AppCompatActivity(), NfcAdapter.ReaderCallback {
         }
     }
 
+    private fun getActiveFragment(): Fragment? {
+        return supportFragmentManager.findFragmentById(R.id.nav_host_fragment)
+                ?.childFragmentManager?.primaryNavigationFragment
+    }
 }
\ No newline at end of file
diff --git a/dependencies.gradle b/dependencies.gradle
index f1121c113d..f4514092a4 100644
--- a/dependencies.gradle
+++ b/dependencies.gradle
@@ -1,4 +1,4 @@
 ext.versions = [
         kotlin      : '1.3.71',
-        build_gradle: '3.6.1',
+        build_gradle: '3.6.2',
 ]