diff --git a/crates/oxc_parser/src/cursor.rs b/crates/oxc_parser/src/cursor.rs
index 59fcf3fea..a33c70816 100644
--- a/crates/oxc_parser/src/cursor.rs
+++ b/crates/oxc_parser/src/cursor.rs
@@ -70,7 +70,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Peek nth token
-    pub fn nth(&mut self, n: usize) -> &Token {
+    pub fn nth(&mut self, n: u8) -> &Token {
         if n == 0 {
             return self.cur_token();
         }
@@ -78,12 +78,12 @@ impl<'a> Parser<'a> {
     }
 
     /// Peek at nth kind
-    pub fn nth_at(&mut self, n: usize, kind: Kind) -> bool {
+    pub fn nth_at(&mut self, n: u8, kind: Kind) -> bool {
         self.nth(n).kind == kind
     }
 
     /// Peek nth kind
-    pub fn nth_kind(&mut self, n: usize) -> Kind {
+    pub fn nth_kind(&mut self, n: u8) -> Kind {
         self.nth(n).kind
     }
 
diff --git a/crates/oxc_parser/src/js/function.rs b/crates/oxc_parser/src/js/function.rs
index 90ebfedf1..9e6da6d55 100644
--- a/crates/oxc_parser/src/js/function.rs
+++ b/crates/oxc_parser/src/js/function.rs
@@ -328,7 +328,7 @@ impl<'a> Parser<'a> {
         &mut self,
         r#async: bool,
     ) -> IsParenthesizedArrowFunction {
-        let offset = usize::from(r#async);
+        let offset = u8::from(r#async);
 
         match self.nth_kind(offset) {
             Kind::LParen => match self.nth_kind(offset + 1) {
diff --git a/crates/oxc_parser/src/lexer/mod.rs b/crates/oxc_parser/src/lexer/mod.rs
index 23e8c28d4..302850b41 100644
--- a/crates/oxc_parser/src/lexer/mod.rs
+++ b/crates/oxc_parser/src/lexer/mod.rs
@@ -114,7 +114,8 @@ impl<'a> Lexer<'a> {
     }
 
     /// Find the nth lookahead token lazily
-    pub fn lookahead(&mut self, n: usize) -> &Token {
+    pub fn lookahead(&mut self, n: u8) -> &Token {
+        let n = n as usize;
         debug_assert!(n > 0);
 
         if self.lookahead.len() > n - 1 {
diff --git a/crates/oxc_parser/src/ts/statement.rs b/crates/oxc_parser/src/ts/statement.rs
index cb5097799..23d7a6601 100644
--- a/crates/oxc_parser/src/ts/statement.rs
+++ b/crates/oxc_parser/src/ts/statement.rs
@@ -183,7 +183,7 @@ impl<'a> Parser<'a> {
         self.nth_at(offset + 2, Kind::Colon)
     }
 
-    pub fn is_nth_at_modifier(&mut self, n: usize, is_constructor_parameter: bool) -> bool {
+    pub fn is_nth_at_modifier(&mut self, n: u8, is_constructor_parameter: bool) -> bool {
         let nth = self.nth(n);
         if !(matches!(
             nth.kind,
@@ -299,7 +299,7 @@ impl<'a> Parser<'a> {
             .map(|decl| Statement::Declaration(Declaration::TSModuleDeclaration(decl)))
     }
 
-    pub fn is_nth_at_ts_namespace_declaration(&mut self, n: usize) -> bool {
+    pub fn is_nth_at_ts_namespace_declaration(&mut self, n: u8) -> bool {
         if self.nth(n + 1).is_on_new_line {
             return false;
         }
diff --git a/crates/oxc_parser/src/ts/types.rs b/crates/oxc_parser/src/ts/types.rs
index fe73b80b9..509b0b379 100644
--- a/crates/oxc_parser/src/ts/types.rs
+++ b/crates/oxc_parser/src/ts/types.rs
@@ -616,7 +616,7 @@ impl<'a> Parser<'a> {
     }
 
     pub fn is_at_named_tuple_element(&mut self) -> bool {
-        let offset = usize::from(self.at(Kind::Dot3));
+        let offset = u8::from(self.at(Kind::Dot3));
         let has_colon = self.nth_at(offset + 1, Kind::Colon);
         let has_question_colon =
             self.nth_at(offset + 1, Kind::Question) && self.nth_at(offset + 2, Kind::Colon);