diff --git a/src/IOThread.cxx b/src/IOThread.cxx
index a7782a0f0..7f0a93aed 100644
--- a/src/IOThread.cxx
+++ b/src/IOThread.cxx
@@ -100,9 +100,3 @@ io_thread_get()
 
 	return *io.loop;
 }
-
-bool
-io_thread_inside(void)
-{
-	return io.thread.IsInside();
-}
diff --git a/src/IOThread.hxx b/src/IOThread.hxx
index 1c19c634e..97a682799 100644
--- a/src/IOThread.hxx
+++ b/src/IOThread.hxx
@@ -45,11 +45,4 @@ gcc_const
 EventLoop &
 io_thread_get();
 
-/**
- * Is the current thread the I/O thread?
- */
-gcc_pure
-bool
-io_thread_inside();
-
 #endif