diff --git a/src/main/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFrom.java b/src/main/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFrom.java
index e410733888..59872e836e 100644
--- a/src/main/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFrom.java
+++ b/src/main/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFrom.java
@@ -13,14 +13,14 @@
 
 package io.reactivex.internal.operators.flowable;
 
-import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.atomic.*;
 
 import org.reactivestreams.*;
 
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.functions.BiFunction;
-import io.reactivex.internal.subscriptions.*;
-import io.reactivex.plugins.RxJavaPlugins;
+import io.reactivex.internal.functions.ObjectHelper;
+import io.reactivex.internal.subscriptions.SubscriptionHelper;
 import io.reactivex.subscribers.SerializedSubscriber;
 
 public final class FlowableWithLatestFrom<T, U, R> extends AbstractFlowableWithUpstream<T, R> {
@@ -37,6 +37,8 @@ protected void subscribeActual(Subscriber<? super R> s) {
         final SerializedSubscriber<R> serial = new SerializedSubscriber<R>(s);
         final WithLatestFromSubscriber<T, U, R> wlf = new WithLatestFromSubscriber<T, U, R>(serial, combiner);
 
+        serial.onSubscribe(wlf);
+
         other.subscribe(new Subscriber<U>() {
             @Override
             public void onSubscribe(Subscription s) {
@@ -73,6 +75,8 @@ static final class WithLatestFromSubscriber<T, U, R> extends AtomicReference<U>
 
         final AtomicReference<Subscription> s = new AtomicReference<Subscription>();
 
+        final AtomicLong requested = new AtomicLong();
+
         final AtomicReference<Subscription> other = new AtomicReference<Subscription>();
 
         WithLatestFromSubscriber(Subscriber<? super R> actual, BiFunction<? super T, ? super U, ? extends R> combiner) {
@@ -81,9 +85,7 @@ static final class WithLatestFromSubscriber<T, U, R> extends AtomicReference<U>
         }
         @Override
         public void onSubscribe(Subscription s) {
-            if (SubscriptionHelper.setOnce(this.s, s)) {
-                actual.onSubscribe(this);
-            }
+            SubscriptionHelper.deferredSetOnce(this.s, requested, s);
         }
 
         @Override
@@ -92,7 +94,7 @@ public void onNext(T t) {
             if (u != null) {
                 R r;
                 try {
-                    r = combiner.apply(t, u);
+                    r = ObjectHelper.requireNonNull(combiner.apply(t, u), "The combiner returned a null value");
                 } catch (Throwable e) {
                     Exceptions.throwIfFatal(e);
                     cancel();
@@ -117,12 +119,12 @@ public void onComplete() {
 
         @Override
         public void request(long n) {
-            s.get().request(n);
+            SubscriptionHelper.deferredRequest(s, requested, n);
         }
 
         @Override
         public void cancel() {
-            s.get().cancel();
+            SubscriptionHelper.cancel(s);
             SubscriptionHelper.cancel(other);
         }
 
@@ -131,16 +133,8 @@ public boolean setOther(Subscription o) {
         }
 
         public void otherError(Throwable e) {
-            if (s.compareAndSet(null, SubscriptionHelper.CANCELLED)) {
-                EmptySubscription.error(e, actual);
-            } else {
-                if (s.get() != SubscriptionHelper.CANCELLED) {
-                    cancel();
-                    actual.onError(e);
-                } else {
-                    RxJavaPlugins.onError(e);
-                }
-            }
+            SubscriptionHelper.cancel(s);
+            actual.onError(e);
         }
     }
 }
diff --git a/src/main/java/io/reactivex/internal/operators/observable/ObservableWithLatestFrom.java b/src/main/java/io/reactivex/internal/operators/observable/ObservableWithLatestFrom.java
index cf36a60641..3f79625910 100644
--- a/src/main/java/io/reactivex/internal/operators/observable/ObservableWithLatestFrom.java
+++ b/src/main/java/io/reactivex/internal/operators/observable/ObservableWithLatestFrom.java
@@ -20,6 +20,7 @@
 import io.reactivex.exceptions.Exceptions;
 import io.reactivex.functions.BiFunction;
 import io.reactivex.internal.disposables.DisposableHelper;
+import io.reactivex.internal.functions.ObjectHelper;
 import io.reactivex.observers.SerializedObserver;
 
 public final class ObservableWithLatestFrom<T, U, R> extends AbstractObservableWithUpstream<T, R> {
@@ -37,7 +38,7 @@ public void subscribeActual(Observer<? super R> t) {
         final SerializedObserver<R> serial = new SerializedObserver<R>(t);
         final WithLatestFromObserver<T, U, R> wlf = new WithLatestFromObserver<T, U, R>(serial, combiner);
 
-        t.onSubscribe(wlf);
+        serial.onSubscribe(wlf);
 
         other.subscribe(new Observer<U>() {
             @Override
@@ -91,7 +92,7 @@ public void onNext(T t) {
             if (u != null) {
                 R r;
                 try {
-                    r = combiner.apply(t, u);
+                    r = ObjectHelper.requireNonNull(combiner.apply(t, u), "The combiner returned a null value");
                 } catch (Throwable e) {
                     Exceptions.throwIfFatal(e);
                     dispose();
diff --git a/src/test/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFromTest.java b/src/test/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFromTest.java
index 9b06cfb156..026f4b863e 100644
--- a/src/test/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFromTest.java
+++ b/src/test/java/io/reactivex/internal/operators/flowable/FlowableWithLatestFromTest.java
@@ -681,4 +681,31 @@ public Integer apply(Integer a, Integer b) throws Exception {
             RxJavaPlugins.reset();
         }
     }
+
+    @Test
+    public void combineToNull1() {
+        Flowable.just(1)
+        .withLatestFrom(Flowable.just(2), new BiFunction<Integer, Integer, Object>() {
+            @Override
+            public Object apply(Integer a, Integer b) throws Exception {
+                return null;
+            }
+        })
+        .test()
+        .assertFailure(NullPointerException.class);
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    public void combineToNull2() {
+        Flowable.just(1)
+        .withLatestFrom(Arrays.asList(Flowable.just(2), Flowable.just(3)), new Function<Object[], Object>() {
+            @Override
+            public Object apply(Object[] o) throws Exception {
+                return null;
+            }
+        })
+        .test()
+        .assertFailure(NullPointerException.class);
+    }
 }
\ No newline at end of file
diff --git a/src/test/java/io/reactivex/internal/operators/observable/ObservableWithLatestFromTest.java b/src/test/java/io/reactivex/internal/operators/observable/ObservableWithLatestFromTest.java
index b4f19c95d7..dae8cfb615 100644
--- a/src/test/java/io/reactivex/internal/operators/observable/ObservableWithLatestFromTest.java
+++ b/src/test/java/io/reactivex/internal/operators/observable/ObservableWithLatestFromTest.java
@@ -21,9 +21,9 @@
 import org.junit.*;
 import org.mockito.InOrder;
 
+import io.reactivex.*;
 import io.reactivex.Observable;
 import io.reactivex.Observer;
-import io.reactivex.TestHelper;
 import io.reactivex.disposables.Disposables;
 import io.reactivex.exceptions.TestException;
 import io.reactivex.functions.*;
@@ -620,4 +620,31 @@ public Object apply(Integer a, Integer b, Integer c) throws Exception {
             RxJavaPlugins.reset();
         }
     }
+
+    @Test
+    public void combineToNull1() {
+        Observable.just(1)
+        .withLatestFrom(Observable.just(2), new BiFunction<Integer, Integer, Object>() {
+            @Override
+            public Object apply(Integer a, Integer b) throws Exception {
+                return null;
+            }
+        })
+        .test()
+        .assertFailure(NullPointerException.class);
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    public void combineToNull2() {
+        Observable.just(1)
+        .withLatestFrom(Arrays.asList(Observable.just(2), Observable.just(3)), new Function<Object[], Object>() {
+            @Override
+            public Object apply(Object[] o) throws Exception {
+                return null;
+            }
+        })
+        .test()
+        .assertFailure(NullPointerException.class);
+    }
 }
\ No newline at end of file