diff --git a/src/option_parser.cpp b/src/option_parser.cpp
index 4c9e332a..5d0cd80b 100644
--- a/src/option_parser.cpp
+++ b/src/option_parser.cpp
@@ -53,6 +53,12 @@ enum
     MERGERFS_OPT_VERSION
   };
 
+enum
+  {
+    OPT_DISCARD = 0,
+    OPT_KEEP    = 1
+  };
+
 static
 void
 _set_option(const std::string &option_,