diff --git a/src/cli.rs b/src/cli.rs
index 980060d..f07b513 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -15,7 +15,7 @@ pub fn get_matches() -> ArgMatches {
                     value
                         .parse::<u16>()
                         .map(|port| PORT_RANGE.contains(&port))
-                        .map_err(|e| e.to_string())
+                        .map_err(|err| err.to_string())
                         .and_then(|result| match result {
                             true => Ok(()),
                             false => Err(format!(