diff --git a/borgmatic/hooks/zabbix.py b/borgmatic/hooks/zabbix.py
index 774565ed..b33ce752 100644
--- a/borgmatic/hooks/zabbix.py
+++ b/borgmatic/hooks/zabbix.py
@@ -67,7 +67,7 @@ def ping_monitor(hook_config, config, config_filename, state, monitoring_log_lev
     elif username and password is not None:
         logger.info(f'{config_filename}: Using user/pass auth with user {username} for Zabbix')
         if not dry_run:
-            response = requests.post(base_url, headers=headers, data='{"jsonrpc":"2.0","method":"user.login","params":{"username":"'+username+'","password":"'+password+'"},"id":1}')
+            response = requests.post(base_url, headers=headers, data=f'{{"jsonrpc":"2.0","method":"user.login","params":{{"username":"{username}","password":"{password}"}},"id":1}}')
             data['auth'] = response.json().get('result')
 
     elif username is not None: