diff --git a/mcs/class/System.Net.Http/CFContentStream.cs b/mcs/class/System.Net.Http/CFContentStream.cs
index a5d237d1530958590293115a0d5e75604c49bfac..d8bba8f0f9a9b32851a3b275dbd287e858cdf36f 100644
--- a/mcs/class/System.Net.Http/CFContentStream.cs
+++ b/mcs/class/System.Net.Http/CFContentStream.cs
@@ -97,7 +97,7 @@ namespace System.Net.Http
 			if (gotMutex) {
 				var stream = (CFHTTPStream)sender;
 				if (e.EventType == CFStreamEventType.ErrorOccurred)
-					Volatile.Write (http_exception, ExceptionDispatchInfo.Capture (stream.GetError ()));
+					Volatile.Write (ref http_exception, ExceptionDispatchInfo.Capture (stream.GetError ()));
 				data_mutex.ReleaseMutex ();
 			}
 		}