diff --git a/vm/src/builtins.rs b/vm/src/builtins.rs
index 3d6a6b44e..b4663ddf8 100644
--- a/vm/src/builtins.rs
+++ b/vm/src/builtins.rs
@@ -161,10 +161,12 @@ fn builtin_len(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
 // builtin_list
 
 fn builtin_locals(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
+    if args.args.len() != 0 {
+        panic!("locals() doesn't take any arguments");
+    }
     Ok(vm.get_locals())
 }
 
-
 pub fn builtin_print(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
     trace!("print called with {:?}", args);
     for a in args.args {