diff --git a/mailman_sync.py b/mailman_sync.py
index 93786c4..6acc4d5 100755
--- a/mailman_sync.py
+++ b/mailman_sync.py
@@ -11,12 +11,14 @@ import subprocess
 import requests
 
 
-def sync_members(mailman_bin: Path, mailing_list: str, members: list[str]):
+def sync_members(
+    mailman_bin: Path, mailing_list: str, members: list[str], dry_run: bool
+):
     members_data = "\n".join(members)
     output = subprocess.run(
         [
             mailman_bin / "sync_members",
-            "--no-change",
+            "--no-change" if dry_run else "",
             "--welcome-msg=no",
             "--goodbye-msg=no",
             "--notifyadmin=no",
@@ -32,7 +34,7 @@ def sync_members(mailman_bin: Path, mailing_list: str, members: list[str]):
     print(output.stdout)
 
 
-def main(mailman_bin: Path, api: str, token: str, list_suffix: str):
+def main(mailman_bin: Path, api: str, token: str, list_suffix: str, dry_run: bool):
     r = requests.get(api, headers={"Authorization": "Token " + token})
     if not r.ok:
         print(f"Failed to get mailing list data from api: {r.status_code} {r.text}")
@@ -48,7 +50,7 @@ def main(mailman_bin: Path, api: str, token: str, list_suffix: str):
     for name, members in certification_lists.items():
         list_name = name + list_suffix
         if list_name in existing_lists:
-            sync_members(mailman_bin, list_name, members)
+            sync_members(mailman_bin, list_name, members, dry_run)
         else:
             print(f"Skipping {list_name}, as it does not exist in Mailman")
 
@@ -64,10 +66,16 @@ if __name__ == "__main__":
     argp.add_argument("--api", required=True, help="API endpoint to retrieve JSON from")
     argp.add_argument("--token", required=True, help="Authorization Token for API")
     argp.add_argument("--list-suffix", help="Suffix for mailing lists")
+    argp.add_argument(
+        "-n",
+        "--dry-run",
+        action="store_true",
+        help="Don't make changes, just print what would happen",
+    )
     args = argp.parse_args()
 
     try:
-        main(args.bin, args.api, args.token, args.list_suffix)
+        main(args.bin, args.api, args.token, args.list_suffix, args.dry_run)
     except subprocess.CalledProcessError as e:
         print(e.stderr)
         raise