diff --git a/src/OpenTracing.Contrib.NetCore/CoreFx/HttpHandlerDiagnostics.cs b/src/OpenTracing.Contrib.NetCore/CoreFx/HttpHandlerDiagnostics.cs
index 86af255..eb78115 100644
--- a/src/OpenTracing.Contrib.NetCore/CoreFx/HttpHandlerDiagnostics.cs
+++ b/src/OpenTracing.Contrib.NetCore/CoreFx/HttpHandlerDiagnostics.cs
@@ -112,7 +112,7 @@ protected override void OnNext(string eventName, object arg)
 
                             span.Finish();
 
-                            request.Properties[PropertiesKey] = null;
+                            request.Properties.Remove(PropertiesKey);
                         }
                     }
                     break;