@@ -26,10 +26,14 @@
 
 @implementation OFStream
 - init
 {
 	self = [super init];
+
+	if (isa == [OFStream class])
+		@throw [OFNotImplementedException newWithClass: isa
+						      selector: _cmd];
 
 	cache = NULL;
 
 #ifndef _WIN32
 	if (pagesize == 0)