diff --git a/tools/as.py b/tools/as.py
index 3cc60b0..d3b56a8 100644
--- a/tools/as.py
+++ b/tools/as.py
@@ -37,6 +37,8 @@ class AsTransformer(lark.Transformer):
 
     def statement(self, s):
         opcode, *params = s
+        if params[0] is None:
+            params = []
         addr = self.addr
         self.addr += 2
         return ('OP', addr, opcode, *params)