diff --git a/clvm_tools/binutils.py b/clvm_tools/binutils.py
index be611f1..3a5c56c 100644
--- a/clvm_tools/binutils.py
+++ b/clvm_tools/binutils.py
@@ -1,7 +1,9 @@
 import string
+from typing import Dict
 
 from clvm import KEYWORD_FROM_ATOM, KEYWORD_TO_ATOM
 from clvm.casts import int_from_bytes, int_to_bytes
+from clvm.SExp import SExp
 
 from ir.reader import read_ir
 from ir.writer import write_ir
@@ -80,7 +82,7 @@ def disassemble_to_ir(sexp, keyword_from_atom, allow_keyword=None):
     return sexp.to((type_for_atom(as_atom), as_atom))
 
 
-def disassemble(sexp, keyword_from_atom=KEYWORD_FROM_ATOM):
+def disassemble(sexp: SExp, keyword_from_atom: Dict[bytes, str] = KEYWORD_FROM_ATOM) -> str:
     symbols = disassemble_to_ir(sexp, keyword_from_atom=keyword_from_atom)
     return write_ir(symbols)