diff --git a/src/umbraco.cms/businesslogic/ContentType.cs b/src/umbraco.cms/businesslogic/ContentType.cs
index 2154ec0118..bd136b1b44 100644
--- a/src/umbraco.cms/businesslogic/ContentType.cs
+++ b/src/umbraco.cms/businesslogic/ContentType.cs
@@ -144,7 +144,8 @@ namespace umbraco.cms.businesslogic
                 }
                 foreach (Tuple<string, string> key in toDelete)
                 {
-                    _propertyTypeCache.Remove(key);
+                    if(_propertyTypeCache.ContainsKey(key))
+                        _propertyTypeCache.Remove(key);
                 }				
             }
 			//don't put lock around this as it is ConcurrentDictionary.