diff --git a/aftltool.py b/aftltool.py
index 936fe98..b695d16 100755
--- a/aftltool.py
+++ b/aftltool.py
@@ -48,7 +48,7 @@
 import avbtool
 import aftl_pb2
 import api_pb2
-from crypto import sigpb
+from crypto.sigpb import sigpb_pb2
 # pylint: enable=wrong-import-position,import-error
 
 
@@ -1354,7 +1354,7 @@
     except avbtool.AvbError as e:
       raise AftlError('Failed to sign FirmwareInfo with '
                       '--manufacturer_key: {}'.format(e))
-    fw_info_sig = sigpb.sigpb_pb2.DigitallySigned(
+    fw_info_sig = sigpb_pb2.DigitallySigned(
         hash_algorithm='SHA256',
         signature_algorithm='RSA',
         signature=signed_fw_info)
@@ -1559,6 +1559,7 @@
     if not stats_filename:
       stats_filename = 'load_test_p{}_s{}.csv'.format(process_count,
                                                       submission_count)
+    stats_file = None
     try:
       stats_file = open(stats_filename, 'w')
       stats_file.write('start_time,end_time,execution_time,version_incremental,'
diff --git a/avbtool.py b/avbtool.py
index dad60d6..4b9c594 100755
--- a/avbtool.py
+++ b/avbtool.py
@@ -3141,7 +3141,7 @@
 
       # Calculate the signature.
       rsa_key = RSAPublicKey(key_path)
-      data_to_sign = header_data_blob + aux_data_blob
+      data_to_sign = header_data_blob + bytes(aux_data_blob)
       binary_signature = rsa_key.sign(algorithm_name, data_to_sign,
                                       signing_helper, signing_helper_with_files)