diff --git a/android/guava/src/com/google/common/collect/ImmutableClassToInstanceMap.java b/android/guava/src/com/google/common/collect/ImmutableClassToInstanceMap.java
index 5c907f7cd468..0ad82e917a70 100644
--- a/android/guava/src/com/google/common/collect/ImmutableClassToInstanceMap.java
+++ b/android/guava/src/com/google/common/collect/ImmutableClassToInstanceMap.java
@@ -123,7 +123,7 @@ public <T extends B> Builder<B> putAll(Map<? extends Class<? extends T>, ? exten
       return this;
     }
 
-    private static <B, T extends B> T cast(Class<T> type, B value) {
+    private static <T> T cast(Class<T> type, Object value) {
       return Primitives.wrap(type).cast(value);
     }
 
diff --git a/android/guava/src/com/google/common/collect/MutableClassToInstanceMap.java b/android/guava/src/com/google/common/collect/MutableClassToInstanceMap.java
index 0111ccade791..ea5199561e6e 100644
--- a/android/guava/src/com/google/common/collect/MutableClassToInstanceMap.java
+++ b/android/guava/src/com/google/common/collect/MutableClassToInstanceMap.java
@@ -96,7 +96,8 @@ private MutableClassToInstanceMap(Map<Class<? extends @NonNull B>, B> delegate)
       @Override
       @ParametricNullness
       public B setValue(@ParametricNullness B value) {
-        return super.setValue(cast(getKey(), value));
+        cast(getKey(), value);
+        return super.setValue(value);
       }
     };
   }
@@ -148,7 +149,8 @@ public Object[] toArray() {
   @CanIgnoreReturnValue
   @CheckForNull
   public B put(Class<? extends @NonNull B> key, @ParametricNullness B value) {
-    return super.put(key, cast(key, value));
+    cast(key, value);
+    return super.put(key, value);
   }
 
   @Override
@@ -175,7 +177,7 @@ public <T extends B> T putInstance(Class<@NonNull T> type, @ParametricNullness T
 
   @CanIgnoreReturnValue
   @CheckForNull
-  private static <B, T extends B> T cast(Class<@NonNull T> type, @CheckForNull B value) {
+  private static <T> T cast(Class<T> type, @CheckForNull Object value) {
     return Primitives.wrap(type).cast(value);
   }
 
diff --git a/android/guava/src/com/google/common/util/concurrent/MoreExecutors.java b/android/guava/src/com/google/common/util/concurrent/MoreExecutors.java
index b3b22865095b..450d2b296bda 100644
--- a/android/guava/src/com/google/common/util/concurrent/MoreExecutors.java
+++ b/android/guava/src/com/google/common/util/concurrent/MoreExecutors.java
@@ -16,6 +16,7 @@
 
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
+import static java.util.Objects.requireNonNull;
 
 import com.google.common.annotations.Beta;
 import com.google.common.annotations.GwtCompatible;
@@ -891,7 +892,8 @@ private static boolean isAppEngineWithApiClasses() {
   static Thread newThread(String name, Runnable runnable) {
     checkNotNull(name);
     checkNotNull(runnable);
-    Thread result = platformThreadFactory().newThread(runnable);
+    // TODO(b/139726489): Confirm that null is impossible here.
+    Thread result = requireNonNull(platformThreadFactory().newThread(runnable));
     try {
       result.setName(name);
     } catch (SecurityException e) {
diff --git a/android/guava/src/com/google/common/util/concurrent/ThreadFactoryBuilder.java b/android/guava/src/com/google/common/util/concurrent/ThreadFactoryBuilder.java
index c0116f80b3d1..80727c59a8d7 100644
--- a/android/guava/src/com/google/common/util/concurrent/ThreadFactoryBuilder.java
+++ b/android/guava/src/com/google/common/util/concurrent/ThreadFactoryBuilder.java
@@ -171,6 +171,8 @@ private static ThreadFactory doBuild(ThreadFactoryBuilder builder) {
       @Override
       public Thread newThread(Runnable runnable) {
         Thread thread = backingThreadFactory.newThread(runnable);
+        // TODO(b/139735208): Figure out what to do when the factory returns null.
+        requireNonNull(thread);
         if (nameFormat != null) {
           // requireNonNull is safe because we create `count` if (and only if) we have a nameFormat.
           thread.setName(format(nameFormat, requireNonNull(count).getAndIncrement()));
diff --git a/guava/src/com/google/common/collect/ImmutableClassToInstanceMap.java b/guava/src/com/google/common/collect/ImmutableClassToInstanceMap.java
index 5c907f7cd468..0ad82e917a70 100644
--- a/guava/src/com/google/common/collect/ImmutableClassToInstanceMap.java
+++ b/guava/src/com/google/common/collect/ImmutableClassToInstanceMap.java
@@ -123,7 +123,7 @@ public <T extends B> Builder<B> putAll(Map<? extends Class<? extends T>, ? exten
       return this;
     }
 
-    private static <B, T extends B> T cast(Class<T> type, B value) {
+    private static <T> T cast(Class<T> type, Object value) {
       return Primitives.wrap(type).cast(value);
     }
 
diff --git a/guava/src/com/google/common/collect/MutableClassToInstanceMap.java b/guava/src/com/google/common/collect/MutableClassToInstanceMap.java
index 740d66715bcc..98b4026142e3 100644
--- a/guava/src/com/google/common/collect/MutableClassToInstanceMap.java
+++ b/guava/src/com/google/common/collect/MutableClassToInstanceMap.java
@@ -97,7 +97,8 @@ private MutableClassToInstanceMap(Map<Class<? extends @NonNull B>, B> delegate)
       @Override
       @ParametricNullness
       public B setValue(@ParametricNullness B value) {
-        return super.setValue(cast(getKey(), value));
+        cast(getKey(), value);
+        return super.setValue(value);
       }
     };
   }
@@ -155,7 +156,8 @@ public Object[] toArray() {
   @CanIgnoreReturnValue
   @CheckForNull
   public B put(Class<? extends @NonNull B> key, @ParametricNullness B value) {
-    return super.put(key, cast(key, value));
+    cast(key, value);
+    return super.put(key, value);
   }
 
   @Override
@@ -182,7 +184,7 @@ public <T extends B> T putInstance(Class<@NonNull T> type, @ParametricNullness T
 
   @CanIgnoreReturnValue
   @CheckForNull
-  private static <B, T extends B> T cast(Class<@NonNull T> type, @CheckForNull B value) {
+  private static <T> T cast(Class<T> type, @CheckForNull Object value) {
     return Primitives.wrap(type).cast(value);
   }
 
diff --git a/guava/src/com/google/common/util/concurrent/MoreExecutors.java b/guava/src/com/google/common/util/concurrent/MoreExecutors.java
index 55a778a5c213..d244254eb513 100644
--- a/guava/src/com/google/common/util/concurrent/MoreExecutors.java
+++ b/guava/src/com/google/common/util/concurrent/MoreExecutors.java
@@ -17,6 +17,7 @@
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.util.concurrent.Internal.toNanosSaturated;
+import static java.util.Objects.requireNonNull;
 
 import com.google.common.annotations.Beta;
 import com.google.common.annotations.GwtCompatible;
@@ -972,7 +973,8 @@ private static boolean isAppEngineWithApiClasses() {
   static Thread newThread(String name, Runnable runnable) {
     checkNotNull(name);
     checkNotNull(runnable);
-    Thread result = platformThreadFactory().newThread(runnable);
+    // TODO(b/139726489): Confirm that null is impossible here.
+    Thread result = requireNonNull(platformThreadFactory().newThread(runnable));
     try {
       result.setName(name);
     } catch (SecurityException e) {
diff --git a/guava/src/com/google/common/util/concurrent/ThreadFactoryBuilder.java b/guava/src/com/google/common/util/concurrent/ThreadFactoryBuilder.java
index c0116f80b3d1..80727c59a8d7 100644
--- a/guava/src/com/google/common/util/concurrent/ThreadFactoryBuilder.java
+++ b/guava/src/com/google/common/util/concurrent/ThreadFactoryBuilder.java
@@ -171,6 +171,8 @@ private static ThreadFactory doBuild(ThreadFactoryBuilder builder) {
       @Override
       public Thread newThread(Runnable runnable) {
         Thread thread = backingThreadFactory.newThread(runnable);
+        // TODO(b/139735208): Figure out what to do when the factory returns null.
+        requireNonNull(thread);
         if (nameFormat != null) {
           // requireNonNull is safe because we create `count` if (and only if) we have a nameFormat.
           thread.setName(format(nameFormat, requireNonNull(count).getAndIncrement()));