diff --git a/owrx/wsjt.py b/owrx/wsjt.py
index 8ea00bc..982e475 100644
--- a/owrx/wsjt.py
+++ b/owrx/wsjt.py
@@ -11,7 +11,7 @@ from owrx.config import Config
 from owrx.metrics import Metrics, CounterMetric, DirectMetric
 from owrx.pskreporter import PskReporter
 from owrx.parser import Parser
-from abc import ABCMeta, abstractmethod
+from abc import ABC, ABCMeta, abstractmethod
 
 import logging
 
@@ -333,13 +333,17 @@ class WsjtParser(Parser):
         metric.inc()
 
 
-class Decoder(object):
+class Decoder(ABC):
     def parse_timestamp(self, instring, dateformat):
         ts = datetime.strptime(instring, dateformat)
         return int(
             datetime.combine(datetime.utcnow().date(), ts.time()).replace(tzinfo=timezone.utc).timestamp() * 1000
         )
 
+    @abstractmethod
+    def parse(self, msg, dial_freq):
+        pass
+
 
 class Jt9Decoder(Decoder):
     locator_pattern = re.compile("[A-Z0-9]+\\s([A-Z0-9]+)\\s([A-R]{2}[0-9]{2})$")