diff --git a/src/main/java/org/anarres/parallelgzip/ParallelGZIPOutputStream.java b/src/main/java/org/anarres/parallelgzip/ParallelGZIPOutputStream.java
index c0abf30..894d591 100644
--- a/src/main/java/org/anarres/parallelgzip/ParallelGZIPOutputStream.java
+++ b/src/main/java/org/anarres/parallelgzip/ParallelGZIPOutputStream.java
@@ -230,7 +230,7 @@ public void write(byte[] b, int off, int len) throws IOException {
     // Master thread only
     private void submit() throws IOException {
         emitUntil(emitQueueSize - 1);
-        emitQueue.add(executor.submit(block));
+        emitQueue.put(executor.submit(block));
         Block b = freeBlock;
         if (b != null)
             freeBlock = null;