diff --git a/changelog.d/12789.misc b/changelog.d/12789.misc
new file mode 100644
index 0000000000..3398d00110
--- /dev/null
+++ b/changelog.d/12789.misc
@@ -0,0 +1 @@
+The `hash_password` script now fails when it is called without specifying a config file.
diff --git a/synapse/_scripts/hash_password.py b/synapse/_scripts/hash_password.py
index 3aa29de5bd..3bed367be2 100755
--- a/synapse/_scripts/hash_password.py
+++ b/synapse/_scripts/hash_password.py
@@ -46,14 +46,14 @@ def main() -> None:
             "Path to server config file. "
             "Used to read in bcrypt_rounds and password_pepper."
         ),
+        required=True,
     )
 
     args = parser.parse_args()
-    if "config" in args and args.config:
-        config = yaml.safe_load(args.config)
-        bcrypt_rounds = config.get("bcrypt_rounds", bcrypt_rounds)
-        password_config = config.get("password_config", None) or {}
-        password_pepper = password_config.get("pepper", password_pepper)
+    config = yaml.safe_load(args.config)
+    bcrypt_rounds = config.get("bcrypt_rounds", bcrypt_rounds)
+    password_config = config.get("password_config", None) or {}
+    password_pepper = password_config.get("pepper", password_pepper)
     password = args.password
 
     if not password: