diff --git a/juniper/src/parser/lexer.rs b/juniper/src/parser/lexer.rs
index 3eb6a56a4..baefdf0bc 100644
--- a/juniper/src/parser/lexer.rs
+++ b/juniper/src/parser/lexer.rs
@@ -515,15 +515,15 @@ fn is_source_char(c: char) -> bool {
 }
 
 fn is_name_start(c: char) -> bool {
-    c == '_' || ('A'..='Z').contains(&c) || ('a'..='z').contains(&c)
+    c == '_' || c.is_ascii_alphabetic()
 }
 
 fn is_name_cont(c: char) -> bool {
-    is_name_start(c) || ('0'..='9').contains(&c)
+    is_name_start(c) || c.is_ascii_digit()
 }
 
 fn is_number_start(c: char) -> bool {
-    c == '-' || ('0'..='9').contains(&c)
+    c == '-' || c.is_ascii_digit()
 }
 
 impl fmt::Display for LexerError {
diff --git a/juniper/src/types/name.rs b/juniper/src/types/name.rs
index fbf5304df..899137ad7 100644
--- a/juniper/src/types/name.rs
+++ b/juniper/src/types/name.rs
@@ -5,24 +5,13 @@ use std::{
     str::FromStr,
 };
 
-// Helper functions until the corresponding AsciiExt methods
-// stabilise (https://github.com/rust-lang/rust/issues/39658).
-
-fn is_ascii_alphabetic(c: char) -> bool {
-    ('a'..='z').contains(&c) || ('A'..='Z').contains(&c)
-}
-
-fn is_ascii_digit(c: char) -> bool {
-    ('0'..='9').contains(&c)
-}
-
 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct Name(String);
 
 impl Name {
     pub fn is_valid(input: &str) -> bool {
         for (i, c) in input.chars().enumerate() {
-            let is_valid = is_ascii_alphabetic(c) || c == '_' || (i > 0 && is_ascii_digit(c));
+            let is_valid = c.is_ascii_alphabetic() || c == '_' || (i > 0 && c.is_ascii_digit());
             if !is_valid {
                 return false;
             }