@@ -73,11 +73,11 @@
 #if !defined(HAVE_STRERROR_R) && defined(OF_HAVE_THREADS)
 static of_mutex_t mutex;
 
 OF_CONSTRUCTOR()
 {
-	if (!of_mutex_new(&mutex))
+	if (of_mutex_new(&mutex) != 0)
 		@throw [OFInitializationFailedException exception];
 }
 #endif
 
 OFString *
@@ -187,21 +187,21 @@
 
 	ret = [OFString stringWithCString: buffer
 				 encoding: [OFLocale encoding]];
 #else
 # ifdef OF_HAVE_THREADS
-	if (!of_mutex_lock(&mutex))
+	if (of_mutex_lock(&mutex) != 0)
 		@throw [OFLockFailedException exception];
 
 	@try {
 # endif
 		ret = [OFString
 		    stringWithCString: strerror(errNo)
 			     encoding: [OFLocale encoding]];
 # ifdef OF_HAVE_THREADS
 	} @finally {
-		if (!of_mutex_unlock(&mutex))
+		if (of_mutex_unlock(&mutex) != 0)
 			@throw [OFUnlockFailedException exception];
 	}
 # endif
 #endif