diff --git a/bitcoinlib/transactions.py b/bitcoinlib/transactions.py
index 6894e70f..22ce2c4b 100644
--- a/bitcoinlib/transactions.py
+++ b/bitcoinlib/transactions.py
@@ -1498,7 +1498,9 @@ def parse_bytesio(cls, rawtx, strict=True, network=DEFAULT_NETWORK):
                 inputs[n].script = script if not inputs[n].script else inputs[n].script + script
                 inputs[n].keys = script.keys
                 inputs[n].signatures = script.signatures
-                if script.script_types[0][:13] == 'p2sh_multisig' or script.script_types[0] =='signature_multisig':
+                if not script.signatures:
+                    inputs[n].script_type = 'unknown'
+                elif script.script_types[0][:13] == 'p2sh_multisig' or script.script_types[0] =='signature_multisig':
                     inputs[n].script_type = 'p2sh_multisig'
                     inputs[n].redeemscript = inputs[n].witnesses[-1]
                 elif script.script_types[0] == 'p2tr_unlock':