diff --git a/tools/firmware_hash.py b/tools/firmware_hash.py
index 96fa288e1..b38b7131b 100755
--- a/tools/firmware_hash.py
+++ b/tools/firmware_hash.py
@@ -6,24 +6,42 @@ from hashlib import blake2s
 FILE_T1 = "legacy/firmware/trezor.bin"
 FILE_T2 = "core/build/firmware/firmware.bin"
 
+T1_HEADER_MAGIC_OLD = b"TRZR"
+T1_HEADER_OLD_SIZE = 256
+T2_HEADER_MAGIC_VENDOR = b"TRZV"
+
 SIZE_T1 = (7 * 128 + 64) * 1024
 SIZE_T2 = 13 * 128 * 1024
 
-for filename, size in ((FILE_T1, SIZE_T1), (FILE_T2, SIZE_T2)):
+if len(sys.argv) > 2:
+    filenames = sys.argv[2:]
+elif len(sys.argv) == 2:
+    filenames = (FILE_T1, FILE_T2)
+else:
+    print(f"Usage: {sys.argv[0]} HEX_CHALLENGE [FILE]...")
+    print(f"       HEX_CHALLENGE: a 0-32 byte challenge in hexadecimal")
+    exit(1)
+
+
+for filename in filenames:
     try:
         data = open(filename, "rb").read()
     except FileNotFoundError:
         print(f"{filename} not found")
         continue
 
-    if len(data) > size:
-        raise ValueError(filename, "too big")
-    data = data + b"\xff" * (size - len(data))
-
-    if len(sys.argv) > 1:
-        challenge = bytes.fromhex(sys.argv[1])
-        firmware_hash = blake2s(data, key=challenge).hexdigest()
+    offset = 0
+    if data[:4] == T2_HEADER_MAGIC_VENDOR:
+        size = SIZE_T2
     else:
-        firmware_hash = blake2s(data).hexdigest()
+        size = SIZE_T1
+        if data[:4] == T1_HEADER_MAGIC_OLD:
+            offset = T1_HEADER_OLD_SIZE
+
+    if len(data) - offset > size:
+        raise ValueError(filename, "too big")
+    data = data[offset:] + b"\xff" * (size - len(data) + offset)
 
+    challenge = bytes.fromhex(sys.argv[1])
+    firmware_hash = blake2s(data, key=challenge).hexdigest()
     print(f"{filename}: {firmware_hash}")