diff --git a/src/IOThread.cxx b/src/IOThread.cxx
index 252540501..1fa140095 100644
--- a/src/IOThread.cxx
+++ b/src/IOThread.cxx
@@ -35,7 +35,7 @@ static struct {
 	Thread thread;
 } io;
 
-void
+static void
 io_thread_run(void)
 {
 	assert(io_thread_inside());
diff --git a/src/IOThread.hxx b/src/IOThread.hxx
index f769f8ad4..1c19c634e 100644
--- a/src/IOThread.hxx
+++ b/src/IOThread.hxx
@@ -30,14 +30,6 @@ io_thread_init();
 void
 io_thread_start();
 
-/**
- * Run the I/O event loop synchronously in the current thread.  This
- * can be called instead of io_thread_start().  For testing purposes
- * only.
- */
-void
-io_thread_run();
-
 /**
  * Ask the I/O thread to quit, but does not wait for it.  Usually, you
  * don't need to call this function, because io_thread_deinit()