diff --git a/tools/firmware_hash.py b/tools/firmware_hash.py
index cdeedee64..96fa288e1 100755
--- a/tools/firmware_hash.py
+++ b/tools/firmware_hash.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 
+import sys
 from hashlib import blake2s
-from os import sys
 
 FILE_T1 = "legacy/firmware/trezor.bin"
 FILE_T2 = "core/build/firmware/firmware.bin"
@@ -12,12 +12,12 @@ SIZE_T2 = 13 * 128 * 1024
 for filename, size in ((FILE_T1, SIZE_T1), (FILE_T2, SIZE_T2)):
     try:
         data = open(filename, "rb").read()
-    except:
+    except FileNotFoundError:
         print(f"{filename} not found")
         continue
 
     if len(data) > size:
-        raise ValueError(fn, f"{filename} too big")
+        raise ValueError(filename, "too big")
     data = data + b"\xff" * (size - len(data))
 
     if len(sys.argv) > 1: