diff --git a/src/clap_app.rs b/src/clap_app.rs
index e00d074d..b8f159e0 100644
--- a/src/clap_app.rs
+++ b/src/clap_app.rs
@@ -333,8 +333,8 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
                 .hidden_short_help(true)
                 .validator(
                     |t| {
-                        let sign = t.chars().next().unwrap();
-                        let num = if (sign == '+') || (sign == '-') {
+                        let is_offset = t.starts_with('+') || t.starts_with('-');
+                        let num = if is_offset {
                             t.chars().skip(1).collect()
                         } else {
                             t
@@ -342,7 +342,7 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
 
                         num.parse::<u32>()
                             .map_err(|_e| "must be an offset or number")
-                            .and_then(|v| if v == 0 && sign != '+' && sign != '-' {
+                            .and_then(|v| if v == 0 && !is_offset {
                                 Err("terminal width cannot be zero".into())
                             } else {
                                 Ok(())