diff --git a/test/encode_test_driver.h b/test/encode_test_driver.h
index 7b7dd31..e16cf9c 100644
--- a/test/encode_test_driver.h
+++ b/test/encode_test_driver.h
@@ -183,7 +183,10 @@
  protected:
   explicit EncoderTest(const CodecFactory *codec)
       : codec_(codec), abort_(false), init_flags_(0), frame_flags_(0),
-        last_pts_(0) {}
+        last_pts_(0) {
+    // Default to 1 thread.
+    cfg_.g_threads = 1;
+  }
 
   virtual ~EncoderTest() {}