diff --git a/swh/icinga_plugins/base_check.py b/swh/icinga_plugins/base_check.py
index ce60aed..7110a9e 100644
--- a/swh/icinga_plugins/base_check.py
+++ b/swh/icinga_plugins/base_check.py
@@ -1,27 +1,32 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2022  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+from typing import Dict
+
 
 class BaseCheck:
-    def __init__(self, obj):
-        self.warning_threshold = obj.get(
-            "warning_threshold", self.DEFAULT_WARNING_THRESHOLD
+    DEFAULT_WARNING_THRESHOLD = 60
+    DEFAULT_CRITICAL_THRESHOLD = 120
+
+    def __init__(self, obj: Dict[str, str]) -> None:
+        self.warning_threshold = float(
+            obj.get("warning_threshold", self.DEFAULT_WARNING_THRESHOLD)
         )
-        self.critical_threshold = obj.get(
-            "critical_threshold", self.DEFAULT_CRITICAL_THRESHOLD
+        self.critical_threshold = float(
+            obj.get("critical_threshold", self.DEFAULT_CRITICAL_THRESHOLD)
         )
 
     def get_status(self, value):
         if self.critical_threshold and value >= self.critical_threshold:
             return (2, "CRITICAL")
         elif self.warning_threshold and value >= self.warning_threshold:
             return (1, "WARNING")
         else:
             return (0, "OK")
 
     def print_result(self, status_type, status_string, **metrics):
         print(f"{self.TYPE} {status_type} - {status_string}")
         for (metric_name, metric_value) in sorted(metrics.items()):
             print(f"| '{metric_name}' = {metric_value:.2f}s")