@@ -901,11 +901,11 @@
 }
 
 - (void)setPrefix: (OFString*)prefix
      forNamespace: (OFString*)ns_
 {
-	if (prefix == nil || [prefix isEqual: @""])
+	if ([prefix length] == 0)
 		@throw [OFInvalidArgumentException
 		    exceptionWithClass: [self class]
 			      selector: _cmd];
 	if (ns_ == nil)
 		ns_ = @"";