diff --git a/rrl.py b/rrl.py
index 6603833..2d67d99 100644
--- a/rrl.py
+++ b/rrl.py
@@ -17,10 +17,10 @@ class RateLimitExceeded(Exception):
     pass
 
 
-def _get_redis_connection():
+def _get_redis_connection() -> Redis:
     host = os.environ.get("RRL_REDIS_HOST", "localhost")
-    port = os.environ.get("RRL_REDIS_PORT", 6379)
-    db = os.environ.get("RRL_REDIS_DB", 0)
+    port = int(os.environ.get("RRL_REDIS_PORT", 6379))
+    db = int(os.environ.get("RRL_REDIS_DB", 0))
     return Redis(host=host, port=port, db=db)
 
 
@@ -31,13 +31,15 @@ class RateLimiter:
     <zone>:<key>:<day>                  never expires
     """
 
-    def __init__(self, tiers: typing.List[Tier], *, prefix="", use_redis_time=True):
+    def __init__(
+        self, tiers: typing.List[Tier], *, prefix: str = "", use_redis_time: bool = True
+    ):
         self.redis = _get_redis_connection()
         self.tiers = {tier.name: tier for tier in tiers}
         self.prefix = prefix
         self.use_redis_time = use_redis_time
 
-    def check_limit(self, zone: str, key: str, tier_name: str):
+    def check_limit(self, zone: str, key: str, tier_name: str) -> bool:
         if self.use_redis_time:
             timestamp = self.redis.time()[0]
             now = datetime.datetime.fromtimestamp(timestamp)