1 files changed, 13 insertions, 6 deletions
diff --git a/mcs/class/corlib/System.Runtime.Remoting.Lifetime/Lease.cs b/mcs/class/corlib/System.Runtime.Remoting.Lifetime/Lease.cs
index 48a2f721072..bc6be38f12d 100644
--- a/mcs/class/corlib/System.Runtime.Remoting.Lifetime/Lease.cs
+++ b/mcs/class/corlib/System.Runtime.Remoting.Lifetime/Lease.cs
@@ -118,9 +118,15 @@ namespace System.Runtime.Remoting.Lifetime
 
 		public void Register (ISponsor obj, TimeSpan renewalTime)
 		{
-			lock (this) {
-				if (_sponsors == null)
-					_sponsors = new ArrayList();
+			if (_sponsors == null) 
+			{
+				lock (this) {
+					if (_sponsors == null)
+						_sponsors = new ArrayList();
+				}
+			}
+
+			lock (_sponsors.SyncRoot) {
 				_sponsors.Add (obj);
 			}
 
@@ -137,8 +143,9 @@ namespace System.Runtime.Remoting.Lifetime
 
 		public void Unregister (ISponsor obj)
 		{
-			lock (this) {
-				if (_sponsors == null) return;
+			if (_sponsors == null) return;
+			
+			lock (_sponsors.SyncRoot) {
 				_sponsors.Remove (obj);
 			}
 		}
@@ -156,7 +163,7 @@ namespace System.Runtime.Remoting.Lifetime
 			if (_sponsors != null)
 			{
 				_currentState = LeaseState.Renewing;
-				lock (this) {
+				lock (_sponsors.SyncRoot) {
 					_renewingSponsors = new Queue (_sponsors);
 				}
 				CheckNextSponsor ();