diff --git a/dust-lang/src/identifier.rs b/dust-lang/src/identifier.rs
index 4caf0e5..ac8999f 100644
--- a/dust-lang/src/identifier.rs
+++ b/dust-lang/src/identifier.rs
@@ -1,16 +1,36 @@
 use std::{
+    collections::HashMap,
     fmt::{self, Display, Formatter},
-    sync::Arc,
+    sync::{Arc, OnceLock, RwLock},
 };
 
 use serde::{de::Visitor, Deserialize, Serialize};
 
+static IDENTIFIER_CACHE: OnceLock<RwLock<HashMap<String, Identifier>>> = OnceLock::new();
+
+fn identifier_cache<'a>() -> &'a RwLock<HashMap<String, Identifier>> {
+    IDENTIFIER_CACHE.get_or_init(|| RwLock::new(HashMap::new()))
+}
+
 #[derive(Clone, Debug, Hash, Eq, PartialEq, PartialOrd, Ord)]
 pub struct Identifier(Arc<String>);
 
 impl Identifier {
-    pub fn new<T: ToString>(string: T) -> Self {
-        Identifier(Arc::new(string.to_string()))
+    pub fn new(string: &str) -> Self {
+        let cache = identifier_cache();
+
+        if let Some(identifier) = cache.read().unwrap().get(string) {
+            return identifier.clone();
+        }
+
+        let identifier = Identifier(Arc::new(string.to_string()));
+
+        cache
+            .write()
+            .unwrap()
+            .insert(string.to_string(), identifier.clone());
+
+        identifier
     }
 
     pub fn as_str(&self) -> &str {
diff --git a/dust-lang/src/parser/mod.rs b/dust-lang/src/parser/mod.rs
index ae3eee1..df783b7 100644
--- a/dust-lang/src/parser/mod.rs
+++ b/dust-lang/src/parser/mod.rs
@@ -1,8 +1,6 @@
 #[cfg(test)]
 mod tests;
 
-use std::{cell::RefCell, collections::HashMap};
-
 use chumsky::{input::SpannedInput, pratt::*, prelude::*};
 
 use crate::{
@@ -43,21 +41,8 @@ pub fn parser<'src>(
     let comment = select_ref! {
         Token::Comment(_) => {}
     };
-    let identifiers: RefCell<HashMap<&str, Identifier>> = RefCell::new(HashMap::new());
     let identifier = select! {
-        Token::Identifier(text) => {
-            let mut identifiers = identifiers.borrow_mut();
-
-            if let Some(identifier) = identifiers.get(&text) {
-                identifier.clone()
-            } else {
-                let new = Identifier::new(text);
-
-                identifiers.insert(text, new.clone());
-
-                new
-            }
-        }
+        Token::Identifier(text) => Identifier::new(text),
     };
 
     let positioned_identifier = identifier