diff --git a/linux/devices/devicedefinitions/PlocSupervisorDefinitions.h b/linux/devices/devicedefinitions/PlocSupervisorDefinitions.h
index 312f5c14..ac89c8d4 100644
--- a/linux/devices/devicedefinitions/PlocSupervisorDefinitions.h
+++ b/linux/devices/devicedefinitions/PlocSupervisorDefinitions.h
@@ -310,8 +310,8 @@ enum class TmtcManStatusCode : uint32_t {
   BAD_SP_HEADER = 0x608
 };
 
-static constexpr uint16_t APID_MASK_TC = 0x200;
-static constexpr uint16_t APID_MASK_TM = 0x400;
+static constexpr uint16_t APID_MASK_TC = 0x80;
+static constexpr uint16_t APID_MASK_TM = 0x200;
 static constexpr uint16_t APID_MODULE_MASK = 0x7F;
 static const uint16_t SEQUENCE_COUNT_MASK = 0xFFF;
 
@@ -520,7 +520,8 @@ class TcBase : public ploc::SpTcBase {
     }
     std::memset(spParams.buf + ccsds::HEADER_LEN, 0, TIMESTAMP_LEN);
     payloadStart = spParams.buf + ccsds::HEADER_LEN + SECONDARY_HEADER_LEN;
-    payloadStart[supv::PAYLOAD_OFFSET] = serviceId;
+    spParams.buf[ccsds::HEADER_LEN + SECONDARY_HEADER_LEN - 1] = serviceId;
+    spParams.creator.setSecHeaderFlag();
     return returnvalue::OK;
   }
 };