@@ -26,11 +26,13 @@
 
 @class OFStream;
 @class OFMutableArray;
 @class OFMutableDictionary;
 @class OFDataArray;
+#ifdef OF_THREADS
 @class OFMutex;
+#endif
 
 /*!
  * @brief A protocol that needs to be implemented by delegates for
  *	  OFStreamObserver.
  */
@@ -84,11 +86,13 @@
 	id <OFStreamObserverDelegate> delegate;
 	int cancelFD[2];
 #ifdef _WIN32
 	struct sockaddr_in cancelAddr;
 #endif
+#ifdef OF_THREADS
 	OFMutex *mutex;
+#endif
 }
 
 #ifdef OF_HAVE_PROPERTIES
 @property (assign) id <OFStreamObserverDelegate> delegate;
 #endif