diff --git a/modem/command_ping.py b/modem/command_ping.py
index 2a4e316f..01edd438 100644
--- a/modem/command_ping.py
+++ b/modem/command_ping.py
@@ -1,9 +1,13 @@
 from command import TxCommand
+import api_validations
 
 class PingCommand(TxCommand):
 
     def set_params_from_api(self, apiParams):
         self.dxcall = apiParams['dxcall']
+        if not api_validations.validate_freedata_callsign(self.dxcall):
+            self.dxcall = f"{self.dxcall}-0"
+
         return super().set_params_from_api(apiParams)
 
     def build_frame(self):