diff --git a/lib/ResourceInputStream.php b/lib/ResourceInputStream.php
index e3999db..8859daf 100644
--- a/lib/ResourceInputStream.php
+++ b/lib/ResourceInputStream.php
@@ -204,6 +204,11 @@ public function getResource()
         return $this->resource;
     }
 
+    public function setChunkSize(int $chunkSize)
+    {
+        $this->chunkSize = $chunkSize;
+    }
+
     /**
      * References the read watcher, so the loop keeps running in case there's an active read.
      *
diff --git a/lib/ResourceOutputStream.php b/lib/ResourceOutputStream.php
index f34184b..afe0e46 100644
--- a/lib/ResourceOutputStream.php
+++ b/lib/ResourceOutputStream.php
@@ -51,13 +51,13 @@ public function __construct($stream, int $chunkSize = null)
         \stream_set_write_buffer($stream, 0);
 
         $this->resource = $stream;
-        $this->chunkSize = $chunkSize;
+        $this->chunkSize = &$chunkSize;
 
         $writes = $this->writes = new \SplQueue;
         $writable = &$this->writable;
         $resource = &$this->resource;
 
-        $this->watcher = Loop::onWritable($stream, static function ($watcher, $stream) use ($writes, $chunkSize, &$writable, &$resource) {
+        $this->watcher = Loop::onWritable($stream, static function ($watcher, $stream) use ($writes, &$chunkSize, &$writable, &$resource) {
             static $emptyWrites = 0;
 
             try {
@@ -274,6 +274,11 @@ public function getResource()
         return $this->resource;
     }
 
+    public function setChunkSize(int $chunkSize)
+    {
+        $this->chunkSize = $chunkSize;
+    }
+
     public function __destruct()
     {
         if ($this->resource !== null) {
diff --git a/test/ResourceStreamTest.php b/test/ResourceStreamTest.php
index 58d0fa8..6dd966c 100644
--- a/test/ResourceStreamTest.php
+++ b/test/ResourceStreamTest.php
@@ -274,4 +274,19 @@ public function testIssue47()
             $this->assertStringEqualsFile(__FILE__, $buffer);
         });
     }
+
+    public function testSetChunkSize()
+    {
+        Loop::run(function () {
+            list($a, $b) = $this->getStreamPair();
+            $a->setChunkSize(1);
+            $b->setChunkSize(1);
+
+            $this->assertSame(3, yield $a->write('foo'));
+            $this->assertSame('f', yield $b->read());
+
+            $b->setChunkSize(3);
+            $this->assertSame('oo', yield $b->read());
+        });
+    }
 }