diff --git a/okhttp/src/main/java/io/grpc/okhttp/AsyncSink.java b/okhttp/src/main/java/io/grpc/okhttp/AsyncSink.java
index bd1d4762a2..23c5a76c74 100644
--- a/okhttp/src/main/java/io/grpc/okhttp/AsyncSink.java
+++ b/okhttp/src/main/java/io/grpc/okhttp/AsyncSink.java
@@ -85,19 +85,15 @@ final class AsyncSink implements Sink {
       }
       writeEnqueued = true;
     }
-    serializingExecutor.execute(new Runnable() {
+    serializingExecutor.execute(new WriteRunnable() {
       @Override
-      public void run() {
+      public void doRun() throws IOException {
         Buffer buf = new Buffer();
         synchronized (lock) {
           buf.write(buffer, buffer.completeSegmentByteCount());
           writeEnqueued = false;
         }
-        try {
-          sink.write(buf, buf.size());
-        } catch (IOException e) {
-          transportExceptionHandler.onException(e);
-        }
+        sink.write(buf, buf.size());
       }
     });
   }
@@ -113,20 +109,16 @@ final class AsyncSink implements Sink {
       }
       flushEnqueued = true;
     }
-    serializingExecutor.execute(new Runnable() {
+    serializingExecutor.execute(new WriteRunnable() {
       @Override
-      public void run() {
+      public void doRun() throws IOException {
         Buffer buf = new Buffer();
         synchronized (lock) {
           buf.write(buffer, buffer.size());
           flushEnqueued = false;
         }
-        try {
-          sink.write(buf, buf.size());
-          sink.flush();
-        } catch (IOException e) {
-          transportExceptionHandler.onException(e);
-        }
+        sink.write(buf, buf.size());
+        sink.flush();
       }
     });
   }
@@ -147,16 +139,36 @@ final class AsyncSink implements Sink {
       public void run() {
         buffer.close();
         try {
-          sink.close();
+          if (sink != null) {
+            sink.close();
+          }
         } catch (IOException e) {
           transportExceptionHandler.onException(e);
         }
         try {
-          socket.close();
+          if (socket != null) {
+            socket.close();
+          }
         } catch (IOException e) {
           transportExceptionHandler.onException(e);
         }
       }
     });
   }
+
+  private abstract class WriteRunnable implements Runnable {
+    @Override
+    public final void run() {
+      try {
+        if (sink == null) {
+          throw new IOException("Unable to perform write due to unavailable sink.");
+        }
+        doRun();
+      } catch (Exception e) {
+        transportExceptionHandler.onException(e);
+      }
+    }
+
+    public abstract void doRun() throws IOException;
+  }
 }
\ No newline at end of file
diff --git a/okhttp/src/test/java/io/grpc/okhttp/AsyncSinkTest.java b/okhttp/src/test/java/io/grpc/okhttp/AsyncSinkTest.java
index 5a0e848518..b7cb774579 100644
--- a/okhttp/src/test/java/io/grpc/okhttp/AsyncSinkTest.java
+++ b/okhttp/src/test/java/io/grpc/okhttp/AsyncSinkTest.java
@@ -41,10 +41,10 @@ import java.util.concurrent.Executor;
 import okio.Buffer;
 import okio.Sink;
 import okio.Timeout;
-import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
+import org.mockito.ArgumentCaptor;
 import org.mockito.InOrder;
 
 /** Tests for {@link AsyncSink}. */
@@ -58,14 +58,10 @@ public class AsyncSinkTest {
   private final AsyncSink sink =
       AsyncSink.sink(new SerializingExecutor(queueingExecutor), exceptionHandler);
 
-  @Before
-  public void setUp() throws Exception {
-    sink.becomeConnected(mockedSink, socket);
-  }
-
   @Test
   public void noCoalesceRequired() throws IOException {
     Buffer buffer = new Buffer();
+    sink.becomeConnected(mockedSink, socket);
     sink.write(buffer.writeUtf8("hello"), buffer.size());
     sink.flush();
     queueingExecutor.runAll();
@@ -80,6 +76,7 @@ public class AsyncSinkTest {
     byte[] firstData = "a string".getBytes(Charsets.UTF_8);
     byte[] secondData = "a longer string".getBytes(Charsets.UTF_8);
 
+    sink.becomeConnected(mockedSink, socket);
     Buffer buffer = new Buffer();
     sink.write(buffer.write(firstData), buffer.size());
     sink.flush();
@@ -101,6 +98,7 @@ public class AsyncSinkTest {
     byte[] firstData = "a string".getBytes(Charsets.UTF_8);
     byte[] secondData = "a longer string".getBytes(Charsets.UTF_8);
     Buffer buffer = new Buffer().write(firstData);
+    sink.becomeConnected(mockedSink, socket);
     sink.write(buffer, buffer.size());
     sink.flush();
     buffer = new Buffer().write(secondData);
@@ -120,6 +118,7 @@ public class AsyncSinkTest {
     byte[] firstData = "a string".getBytes(Charsets.UTF_8);
     byte[] secondData = "a longer string".getBytes(Charsets.UTF_8);
     Buffer buffer = new Buffer();
+    sink.becomeConnected(mockedSink, socket);
     sink.write(buffer.write(firstData), buffer.size());
     sink.write(buffer.write(secondData), buffer.size());
     sink.flush();
@@ -138,6 +137,7 @@ public class AsyncSinkTest {
         .when(mockedSink).write(any(Buffer.class), anyLong());
     Buffer buffer = new Buffer();
     buffer.writeUtf8("any message");
+    sink.becomeConnected(mockedSink, socket);
     sink.write(buffer, buffer.size());
     sink.flush();
     queueingExecutor.runAll();
@@ -166,6 +166,7 @@ public class AsyncSinkTest {
         .when(mockedSink).write(any(Buffer.class), anyLong());
     Buffer buffer = new Buffer();
     buffer.writeUtf8("any message");
+    sink.becomeConnected(mockedSink, socket);
     sink.write(buffer, buffer.size());
     sink.close();
     queueingExecutor.runAll();
@@ -180,6 +181,7 @@ public class AsyncSinkTest {
 
   @Test
   public void close_flushShouldThrowException() throws IOException {
+    sink.becomeConnected(mockedSink, socket);
     sink.close();
     queueingExecutor.runAll();
     try {
@@ -195,6 +197,7 @@ public class AsyncSinkTest {
   public void flush_shouldThrowIfAlreadyClosed() throws IOException {
     Buffer buffer = new Buffer();
     buffer.writeUtf8("any message");
+    sink.becomeConnected(mockedSink, socket);
     sink.write(buffer, buffer.size());
     sink.close();
     queueingExecutor.runAll();
@@ -210,6 +213,7 @@ public class AsyncSinkTest {
   @Test
   public void write_callSinkIfBufferIsLargerThanSegmentSize() throws IOException {
     Buffer buffer = new Buffer();
+    sink.becomeConnected(mockedSink, socket);
     // OkHttp is using 8192 as segment size.
     int payloadSize = 8192 * 2 - 1;
     int padding = 10;
@@ -240,6 +244,40 @@ public class AsyncSinkTest {
     verify(mockedSink).flush();
   }
 
+  @Test
+  public void writeAndFlush_beforeConnected() throws IOException {
+    Buffer buffer = new Buffer();
+    sink.write(buffer.writeUtf8("hello"), buffer.size());
+    sink.flush();
+    queueingExecutor.runAll();
+
+    verify(mockedSink, never()).write(any(Buffer.class), anyLong());
+    verify(mockedSink, never()).flush();
+
+    ArgumentCaptor<Throwable> captor = ArgumentCaptor.forClass(Throwable.class);
+
+    verify(exceptionHandler).onException(captor.capture());
+
+    Throwable t = captor.getValue();
+    assertThat(t).isInstanceOf(IOException.class);
+    assertThat(t).hasMessageThat().contains("unavailable sink");
+  }
+
+  @Test
+  public void close_multipleCloseShouldNotThrow() throws IOException {
+    sink.becomeConnected(mockedSink, socket);
+
+    sink.close();
+    queueingExecutor.runAll();
+
+    verify(exceptionHandler, never()).onException(any(Throwable.class));
+
+    sink.close();
+    queueingExecutor.runAll();
+
+    verify(exceptionHandler, never()).onException(any(Throwable.class));
+  }
+
   /**
    * Executor queues incoming runnables instead of running it. Runnables can be invoked via {@link
    * QueueingExecutor#runAll} in serial order.