diff --git a/src/interpreter/callable.rs b/src/interpreter/callable.rs
index d6f9e59..bb00afc 100644
--- a/src/interpreter/callable.rs
+++ b/src/interpreter/callable.rs
@@ -11,7 +11,7 @@ pub trait Callable: Debug + ToString {
 
     /// Run the callable in the execution environment with the specified
     /// arguments.
-    fn call(&self, environment: &mut InterpreterState, arguments: Vec<Value>) -> SloxResult<Value>;
+    fn call(&self, callee: &Value, environment: &mut InterpreterState, arguments: Vec<Value>) -> SloxResult<Value>;
 }
 
 /// A reference to a callable.
diff --git a/src/interpreter/functions.rs b/src/interpreter/functions.rs
index 826903e..d45c654 100644
--- a/src/interpreter/functions.rs
+++ b/src/interpreter/functions.rs
@@ -39,7 +39,12 @@ impl Callable for Function {
         self.params.len()
     }
 
-    fn call(&self, es: &mut InterpreterState, arguments: Vec<Value>) -> SloxResult<Value> {
+    fn call(
+        &self,
+        _callee: &Value,
+        es: &mut InterpreterState,
+        arguments: Vec<Value>,
+    ) -> SloxResult<Value> {
         assert_eq!(arguments.len(), self.arity());
         let param_env = InterpreterState {
             environment: Environment::create_child(&self.env),
diff --git a/src/interpreter/interpretable.rs b/src/interpreter/interpretable.rs
index 7144a6b..c938077 100644
--- a/src/interpreter/interpretable.rs
+++ b/src/interpreter/interpretable.rs
@@ -505,7 +505,7 @@ impl ExprNode {
                     ),
                 ))
             } else {
-                Ok(callable.call(es, arg_values)?.into())
+                Ok(callable.call(&callee, es, arg_values)?.into())
             }
         } else {
             error(right_paren, "can only call functions and classes")
diff --git a/src/interpreter/native_fn.rs b/src/interpreter/native_fn.rs
index a0e8719..b868bd1 100644
--- a/src/interpreter/native_fn.rs
+++ b/src/interpreter/native_fn.rs
@@ -20,7 +20,12 @@ impl Callable for Clock {
         0
     }
 
-    fn call(&self, _environment: &mut InterpreterState, _arguments: Vec<Value>) -> SloxResult<Value> {
+    fn call(
+        &self,
+        _callee: &Value,
+        _environment: &mut InterpreterState,
+        _arguments: Vec<Value>,
+    ) -> SloxResult<Value> {
         let now = SystemTime::now();
         let since_epoch = now
             .duration_since(UNIX_EPOCH)