diff --git a/src/eddn/core/DuplicateMessages.py b/src/eddn/core/DuplicateMessages.py
index d2475c7..418c761 100644
--- a/src/eddn/core/DuplicateMessages.py
+++ b/src/eddn/core/DuplicateMessages.py
@@ -6,6 +6,7 @@ import re
 from datetime import datetime, timedelta
 from threading import Lock, Thread
 from time import sleep
+from typing import Dict
 
 import simplejson
 
@@ -17,15 +18,15 @@ class DuplicateMessages(Thread):
 
     max_minutes = Settings.RELAY_DUPLICATE_MAX_MINUTES
 
-    caches = {}
+    caches: Dict = {}
 
     lock = Lock()
 
-    def __init__(self):
+    def __init__(self) -> None:
         super(DuplicateMessages, self).__init__()
         self.daemon = True
 
-    def run(self):
+    def run(self) -> None:
         """Expire duplicate messages."""
         while True:
             sleep(60)
@@ -36,35 +37,37 @@ class DuplicateMessages(Thread):
                     if self.caches[key] + timedelta(minutes=self.max_minutes) < max_time:
                         del self.caches[key]
 
-    def is_duplicated(self, json):
+    def is_duplicated(self, json: Dict) -> bool:
+        """Detect if the given message is in the duplicates cache."""
         with self.lock:
             # Test messages are never duplicate, would be a pain to wait for another test :D
             if re.search('test', json['$schemaRef'], re.I):
                 return False
 
             # Shallow copy, minus headers
-            jsonTest = {
+            json_test = {
                 '$schemaRef': json['$schemaRef'],
                 'message': dict(json['message']),
             }
 
             # Remove timestamp (Mainly to avoid multiple scan messages and faction influences)
-            jsonTest['message'].pop('timestamp')
+            json_test['message'].pop('timestamp')
 
             # Convert journal starPos to avoid software modification in dupe messages
-            if 'StarPos' in jsonTest['message']:
-                jsonTest['message']['StarPos'] = [int(round(x * 32)) for x in jsonTest['message']['StarPos']]
+            if 'StarPos' in json_test['message']:
+                json_test['message']['StarPos'] = [int(round(x * 32)) for x in json_test['message']['StarPos']]
 
             # Prevent journal Docked event with small difference in distance from start
-            if 'DistFromStarLS' in jsonTest['message']:
-                jsonTest['message']['DistFromStarLS'] = int(jsonTest['message']['DistFromStarLS'] + 0.5)
+            if 'DistFromStarLS' in json_test['message']:
+                json_test['message']['DistFromStarLS'] = int(json_test['message']['DistFromStarLS'] + 0.5)
 
             # Remove journal ScanType and DistanceFromArrivalLS (Avoid duplicate scan messages after SAAScanComplete)
-            jsonTest['message'].pop('ScanType', None)
-            jsonTest['message'].pop('DistanceFromArrivalLS', None)
+            json_test['message'].pop('ScanType', None)
+            json_test['message'].pop('DistanceFromArrivalLS', None)
 
-            message = simplejson.dumps(jsonTest, sort_keys=True) # Ensure most duplicate messages will get the same key
-            key     = hashlib.sha256(message).hexdigest()
+            message = simplejson.dumps(json_test, sort_keys=True)  # Ensure most duplicate messages will get the same
+            # key
+            key = hashlib.sha256(message.encode('utf8')).hexdigest()
 
             if key not in self.caches:
                 self.caches[key] = datetime.utcnow()