Make several methods static.
diff --git a/include/json/value.h b/include/json/value.h
index 06a6c0c..b94aeec 100644
--- a/include/json/value.h
+++ b/include/json/value.h
@@ -720,7 +720,7 @@
                     const InArgs& in,
                     InArgs::const_iterator& itInArg,
                     PathArgument::Kind kind);
-  void invalidPath(const JSONCPP_STRING& path, int location);
+  static void invalidPath(const JSONCPP_STRING& path, int location);
 
   Args args_;
 };