diff --git a/src/main/java/it/tdlight/tdlibsession/td/easy/TdEasySettings.java b/src/main/java/it/tdlight/tdlibsession/td/easy/TdEasySettings.java
index 5725b7e..cdc54d7 100644
--- a/src/main/java/it/tdlight/tdlibsession/td/easy/TdEasySettings.java
+++ b/src/main/java/it/tdlight/tdlibsession/td/easy/TdEasySettings.java
@@ -281,7 +281,7 @@ public class TdEasySettings {
 			return this;
 		}
 
-		public FatalErrorHandler getFatalErrorHandler() {
+		public @Nullable FatalErrorHandler getFatalErrorHandler() {
 			return fatalErrorHandler;
 		}
 
diff --git a/src/main/java/it/tdlight/utils/BatchSubscriber.java b/src/main/java/it/tdlight/utils/BatchSubscriber.java
index a51a744..4ce9224 100644
--- a/src/main/java/it/tdlight/utils/BatchSubscriber.java
+++ b/src/main/java/it/tdlight/utils/BatchSubscriber.java
@@ -18,6 +18,7 @@ import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
+import org.jetbrains.annotations.NotNull;
 import org.reactivestreams.Subscription;
 import org.warp.commonutils.log.Logger;
 import org.warp.commonutils.log.LoggerFactory;
@@ -52,7 +53,7 @@ public abstract class BatchSubscriber<T> implements CoreSubscriber<T> {
 	}
 
 	@Override
-	public void onSubscribe(Subscription s) {
+	public void onSubscribe(@NotNull Subscription s) {
 		setOnce(S, this, s);
 	}
 
diff --git a/src/main/java/it/tdlight/utils/BufferTimeOutPublisher.java b/src/main/java/it/tdlight/utils/BufferTimeOutPublisher.java
index 5650fe6..90597bb 100644
--- a/src/main/java/it/tdlight/utils/BufferTimeOutPublisher.java
+++ b/src/main/java/it/tdlight/utils/BufferTimeOutPublisher.java
@@ -5,6 +5,7 @@ package it.tdlight.utils;
  */
 
 import java.time.Duration;
+import org.jetbrains.annotations.NotNull;
 import org.reactivestreams.Publisher;
 import org.reactivestreams.Subscriber;
 import org.reactivestreams.Subscription;
@@ -99,7 +100,7 @@ public class BufferTimeOutPublisher<T> implements Publisher<List<T>> {
 
 		// upstream
 		@Override
-		public void onSubscribe(Subscription s) {
+		public void onSubscribe(@NotNull Subscription s) {
 			this.subscription = s;
 			scheduledFuture = EXECUTOR.scheduleAtFixedRate(this::timeout, 0, this.duration, TimeUnit.MILLISECONDS);
 		}