diff --git a/tests/risk/answer_key.py b/tests/risk/answer_key.py
index a1eb8ecf..50cce87e 100644
--- a/tests/risk/answer_key.py
+++ b/tests/risk/answer_key.py
@@ -51,12 +51,12 @@ LATEST_ANSWER_KEY_URL = ANSWER_KEY_DL_TEMPLATE.format(
 
 
 def answer_key_signature():
-    with open(ANSWER_KEY_PATH, 'r') as f:
+    with open(ANSWER_KEY_PATH, 'rb') as f:
         md5 = hashlib.md5()
-        while True:
+        buf = f.read(1024)
+        md5.update(buf)
+        while buf != b"":
             buf = f.read(1024)
-            if not buf:
-                break
             md5.update(buf)
     return md5.hexdigest()