diff --git a/hisscl/interp.py b/hisscl/interp.py
index 2bb4636..ceed11b 100644
--- a/hisscl/interp.py
+++ b/hisscl/interp.py
@@ -15,10 +15,9 @@ class Block(dict):
         self.labels = labels
         super().__init__()
 
-class Interp:
-    vars: dict[str, typing.Any] = {}
-    
+class Interp:    
     def __init__(self, stream: typing.TextIO, name: str):
+        self.vars: dict[str, typing.Any] = {}
         self.parser = parser.Parser(stream, name)
         
     def __setitem__(self, key, val):
diff --git a/hisscl/lexer.py b/hisscl/lexer.py
index e46d851..8d32dea 100644
--- a/hisscl/lexer.py
+++ b/hisscl/lexer.py
@@ -34,11 +34,10 @@ class ExpectedError(Exception):
         self.expected = expected
 
 class Lexer:
-    pos = ast.Position()
-    prev_pos = ast.Position()
-    unread = ''
-
     def __init__(self, stream: typing.TextIO, name: str):
+        self.pos = pos = ast.Position()
+        self.prev_pos = ast.Position()
+        self.unread = ''
         self.stream = stream
         self.pos.name = name
 
diff --git a/hisscl/parser.py b/hisscl/parser.py
index bedda17..cd5fa4f 100644
--- a/hisscl/parser.py
+++ b/hisscl/parser.py
@@ -15,10 +15,9 @@ class ExpectedError(Exception):
         self.expected = expected
 
 class Parser:
-    _prev: tuple[lexer.Token, ast.Position, str] | None = None
-    
     def __init__(self, stream: TextIO, name: str):
         self.lexer = lexer.Lexer(stream, name)
+        self._prev: tuple[lexer.Token, ast.Position, str] | None = None
         
     def _scan(self) -> tuple[lexer.Token, ast.Position, str]:
         if self._prev is not None: