diff --git a/src/interpreter/environment.py b/src/interpreter/environment.py
index 9fbc51d..496c495 100644
--- a/src/interpreter/environment.py
+++ b/src/interpreter/environment.py
@@ -17,7 +17,7 @@ class Environment:
     def get(self, name: Token) -> Any:
         try:
             return self.values[name.lexeme]
-        except IndexError:
+        except KeyError:
             if self.enclosing is not None:
                 return self.enclosing.get(name)
             raise PebbleRuntimeError(name, f"Undefined variable '{name.lexeme}'.")