diff --git a/src/main/java/com/google/devtools/build/lib/worker/WorkerMultiplexer.java b/src/main/java/com/google/devtools/build/lib/worker/WorkerMultiplexer.java
index dadfdcb7f07869..00af3113f43c75 100644
--- a/src/main/java/com/google/devtools/build/lib/worker/WorkerMultiplexer.java
+++ b/src/main/java/com/google/devtools/build/lib/worker/WorkerMultiplexer.java
@@ -234,7 +234,13 @@ void resetResponseChecker(Integer requestId) throws InterruptedException {
    * {@code workerProcessResponse} and release the semaphore for the {@code WorkerProxy}.
    */
   private void waitResponse() throws InterruptedException, IOException {
-    recordingStream = new RecordingInputStream(process.getInputStream());
+    Subprocess p = this.process;
+    if (p == null || !p.isAlive()) {
+      // Avoid busy-wait for a new process.
+      Thread.sleep(1);
+      return;
+    }
+    recordingStream = new RecordingInputStream(p.getInputStream());
     recordingStream.startRecording(4096);
     WorkResponse parsedResponse = WorkResponse.parseDelimitedFrom(recordingStream);
 
@@ -303,14 +309,14 @@ String getRecordingStreamMessage() {
 
   /** Returns true if this process has died for other reasons than a call to {@code #destroy()}. */
   boolean diedUnexpectedly() {
-    return process != null && !process.isAlive() && !isInterrupted;
+    Subprocess p = this.process; // Protects against this.process getting null.
+    return p != null && !p.isAlive() && !isInterrupted;
   }
 
   /** Returns the exit value of multiplexer's process, if it has exited. */
   Optional<Integer> getExitValue() {
-    return process != null && !process.isAlive()
-        ? Optional.of(process.exitValue())
-        : Optional.empty();
+    Subprocess p = this.process; // Protects against this.process getting null.
+    return p != null && !p.isAlive() ? Optional.of(p.exitValue()) : Optional.empty();
   }
 
   /** For testing only, to verify that maps are cleared after responses are reaped. */
diff --git a/src/test/java/com/google/devtools/build/lib/worker/TestUtils.java b/src/test/java/com/google/devtools/build/lib/worker/TestUtils.java
index b480e5df4b816c..aa4da66b10f827 100644
--- a/src/test/java/com/google/devtools/build/lib/worker/TestUtils.java
+++ b/src/test/java/com/google/devtools/build/lib/worker/TestUtils.java
@@ -162,7 +162,7 @@ public void close() {
 
     @Override
     public boolean isAlive() {
-      return wasDestroyed;
+      return !wasDestroyed;
     }
   }
 }
diff --git a/src/test/java/com/google/devtools/build/lib/worker/WorkerMultiplexerTest.java b/src/test/java/com/google/devtools/build/lib/worker/WorkerMultiplexerTest.java
index 69784c392b15fc..9075e2a458c106 100644
--- a/src/test/java/com/google/devtools/build/lib/worker/WorkerMultiplexerTest.java
+++ b/src/test/java/com/google/devtools/build/lib/worker/WorkerMultiplexerTest.java
@@ -190,7 +190,7 @@ public void testGetResponse_slowProxy()
 
     WorkResponse fakedResponse1 = WorkResponse.newBuilder().setRequestId(3).build();
     WorkResponse fakedResponse2 = WorkResponse.newBuilder().setRequestId(42).build();
-    // Responses can arrive out of order
+    // Responses can arrive out of order, and before the workerproxies are ready to get them.
     fakedResponse2.writeDelimitedTo(workerOutputStream);
     fakedResponse1.writeDelimitedTo(workerOutputStream);
     workerOutputStream.flush();