diff --git a/src/main.rs b/src/main.rs
index c157fdb..4632d7e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -171,6 +171,7 @@ fn main() {
                      string '{VAR}' in each command by the current parameter value.",
                 )
                 .takes_value(true)
+                .allow_hyphen_values(true)
                 .value_names(&["VAR", "MIN", "MAX"]),
         )
         .arg(