diff --git a/mono/metadata/threadpool.c b/mono/metadata/threadpool.c
index 2420c3d..50d2b29 100644
--- a/mono/metadata/threadpool.c
+++ b/mono/metadata/threadpool.c
@@ -25,6 +25,7 @@
 #include <mono/metadata/threadpool-internals.h>
 #include <mono/metadata/exception.h>
 #include <mono/metadata/file-io.h>
+#include <mono/metadata/gc-internal.h>
 #include <mono/metadata/monitor.h>
 #include <mono/metadata/mono-mlist.h>
 #include <mono/metadata/marshal.h>
@@ -129,10 +130,11 @@ typedef struct {
 } ASyncCall;
 
 typedef struct {
-	MonoSemType lock;
+	/* Do NOT move 'first', 'last' or 'unused' around. */
 	MonoMList *first; /* GC root */
-	MonoMList *last;
 	MonoMList *unused; /* Up to 20 chunks. GC root */
+	MonoMList *last;
+	MonoSemType lock;
 	gint head;
 	gint tail;
 	MonoSemType new_job;
@@ -1187,6 +1189,8 @@ mono_thread_pool_init ()
 	gint thread_count;
 	gint cpu_count = mono_cpu_count ();
 	int result;
+	gsize bitmap;
+	void *descr;
 
 	if (tp_inited == 2)
 		return;
@@ -1200,14 +1204,14 @@ mono_thread_pool_init ()
 		}
 	}
 
-	MONO_GC_REGISTER_ROOT (async_tp.first);
-	MONO_GC_REGISTER_ROOT (async_tp.last);
-	MONO_GC_REGISTER_ROOT (async_tp.unused);
-	MONO_GC_REGISTER_ROOT (async_io_tp.first);
-	MONO_GC_REGISTER_ROOT (async_io_tp.unused);
-	MONO_GC_REGISTER_ROOT (async_io_tp.last);
+	bitmap = 7;
+	descr = mono_gc_make_descr_from_bitmap (&bitmap, 2);
+	mono_gc_register_root ((char *) &async_tp, sizeof (gpointer) * 2, descr);
+	mono_gc_register_root ((char *) &async_io_tp, sizeof (gpointer) * 2, descr);
+	bitmap = 1;
+	descr = mono_gc_make_descr_from_bitmap (&bitmap, 1);
+	mono_gc_register_root ((char *) &socket_io_data.sock_to_state, sizeof (gpointer), descr);
 
-	MONO_GC_REGISTER_ROOT (socket_io_data.sock_to_state);
 	InitializeCriticalSection (&socket_io_data.io_lock);
 	if (g_getenv ("MONO_THREADS_PER_CPU") != NULL) {
 		threads_per_cpu = atoi (g_getenv ("MONO_THREADS_PER_CPU"));
@@ -1346,6 +1350,8 @@ mono_thread_pool_cleanup (void)
 			threadpool_kill_idle_threads (&async_io_tp);
 			MONO_SEM_POST (&async_io_tp.lock);
 			MONO_SEM_DESTROY (&async_io_tp.new_job);
+			mono_gc_deregister_root ((char *) &socket_io_data.sock_to_state);
+			mono_gc_deregister_root ((char *) &async_io_tp);
 		}
 	}
 
@@ -1356,6 +1362,7 @@ mono_thread_pool_cleanup (void)
 	wsqs = NULL;
 	LeaveCriticalSection (&wsqs_lock);
 	MONO_SEM_DESTROY (&async_tp.new_job);
+	mono_gc_deregister_root ((char *) &async_tp);
 }
 
 /* Caller must enter &tp->lock */