diff --git a/nac3embedded/src/lib.rs b/nac3embedded/src/lib.rs
index fbbb66b..bb2b9f3 100644
--- a/nac3embedded/src/lib.rs
+++ b/nac3embedded/src/lib.rs
@@ -102,9 +102,10 @@ impl Nac3 {
         let top_level = self.top_level.as_ref().unwrap();
         let instance = {
             let defs = top_level.definitions.read();
-            let class_def = defs[self.resolver.get_identifier_def(&class_name).unwrap().0].write();
+            let class_def = defs[self.resolver.get_identifier_def(class_name.into()).unwrap().0].write();
             let mut method_def = if let TopLevelDef::Class { methods, .. } = &*class_def {
-                if let Some((_name, _unification_key, definition_id)) = methods.iter().find(|method| method.0 == method_name) {
+                println!("{:?}", methods);
+                if let Some((_name, _unification_key, definition_id)) = methods.iter().find(|method| method.0.to_string() == method_name) {
                     defs[definition_id.0].write()
                 } else {
                     return Err(exceptions::PyValueError::new_err("method not found"));
diff --git a/nac3embedded/src/symbol_resolver.rs b/nac3embedded/src/symbol_resolver.rs
index f8fe760..92f0d0c 100644
--- a/nac3embedded/src/symbol_resolver.rs
+++ b/nac3embedded/src/symbol_resolver.rs
@@ -8,20 +8,21 @@ use nac3core::{
     },
 };
 use parking_lot::Mutex;
+use rustpython_parser::ast::StrRef;
 use std::{collections::HashMap, sync::Arc};
 
 pub struct ResolverInternal {
-    pub id_to_type: Mutex<HashMap<String, Type>>,
-    pub id_to_def: Mutex<HashMap<String, DefinitionId>>,
-    pub class_names: Mutex<HashMap<String, Type>>,
+    pub id_to_type: Mutex<HashMap<StrRef, Type>>,
+    pub id_to_def: Mutex<HashMap<StrRef, DefinitionId>>,
+    pub class_names: Mutex<HashMap<StrRef, Type>>,
 }
 
 impl ResolverInternal {
-    pub fn add_id_def(&self, id: String, def: DefinitionId) {
+    pub fn add_id_def(&self, id: StrRef, def: DefinitionId) {
         self.id_to_def.lock().insert(id, def);
     }
 
-    pub fn add_id_type(&self, id: String, ty: Type) {
+    pub fn add_id_type(&self, id: StrRef, ty: Type) {
         self.id_to_type.lock().insert(id, ty);
     }
 }
@@ -29,23 +30,23 @@ impl ResolverInternal {
 pub struct Resolver(pub Arc<ResolverInternal>);
 
 impl SymbolResolver for Resolver {
-    fn get_symbol_type(&self, _: &mut Unifier, _: &PrimitiveStore, str: &str) -> Option<Type> {
-        let ret = self.0.id_to_type.lock().get(str).cloned();
+    fn get_symbol_type(&self, _: &mut Unifier, _: &PrimitiveStore, str: StrRef) -> Option<Type> {
+        let ret = self.0.id_to_type.lock().get(&str).cloned();
         if ret.is_none() {
             // println!("unknown here resolver {}", str);
         }
         ret
     }
 
-    fn get_symbol_value(&self, _: &str) -> Option<SymbolValue> {
+    fn get_symbol_value(&self, _: StrRef) -> Option<SymbolValue> {
         unimplemented!()
     }
 
-    fn get_symbol_location(&self, _: &str) -> Option<Location> {
+    fn get_symbol_location(&self, _: StrRef) -> Option<Location> {
         unimplemented!()
     }
 
-    fn get_identifier_def(&self, id: &str) -> Option<DefinitionId> {
-        self.0.id_to_def.lock().get(id).cloned()
+    fn get_identifier_def(&self, id: StrRef) -> Option<DefinitionId> {
+        self.0.id_to_def.lock().get(&id).cloned()
     }
 }