diff --git a/include/wx/dir.h b/include/wx/dir.h
index f23862e0a9..305411b749 100644
--- a/include/wx/dir.h
+++ b/include/wx/dir.h
@@ -45,6 +45,11 @@ enum wxDirTraverseResult
     wxDIR_CONTINUE          // continue into this directory
 };
 
+#if wxUSE_LONGLONG
+// error code of wxDir::GetTotalSize()
+extern WXDLLIMPEXP_DATA_BASE(const wxULongLong) wxInvalidSize;
+#endif // wxUSE_LONGLONG
+
 // ----------------------------------------------------------------------------
 // wxDirTraverser: helper class for wxDir::Traverse()
 // ----------------------------------------------------------------------------
diff --git a/interface/wx/dir.h b/interface/wx/dir.h
index d9a9c0dae7..e5dbd92109 100644
--- a/interface/wx/dir.h
+++ b/interface/wx/dir.h
@@ -15,6 +15,11 @@ enum wxDirTraverseResult
     wxDIR_CONTINUE      ///< Continue into this directory.
 };
 
+/**
+    The return value of wxDir::GetTotalSize() in case of error.
+*/
+wxULongLong wxInvalidSize;
+
 /**
     @class wxDirTraverser