diff --git a/src/ca/tcpiiu.cpp b/src/ca/tcpiiu.cpp
index 09c9969fa..c5172a1fe 100644
--- a/src/ca/tcpiiu.cpp
+++ b/src/ca/tcpiiu.cpp
@@ -1388,6 +1388,9 @@ void tcpiiu::writeRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
     nciu &chan, unsigned type, arrayElementCount nElem, const void *pValue )
 {
     guard.assertIdenticalMutex ( this->mutex );
+    if ( INVALID_DB_REQ ( type ) ) {
+        throw cacChannel::badType ();
+    }
     comQueSendMsgMinder minder ( this->sendQue, guard );
     this->sendQue.insertRequestWithPayLoad ( CA_PROTO_WRITE,  
         type, nElem, chan.getSID(guard), chan.getCID(guard), pValue,
@@ -1405,6 +1408,9 @@ void tcpiiu::writeNotifyRequest ( epicsGuard < epicsMutex > & guard, // X aCC 43
     if ( ! this->ca_v41_ok ( guard ) ) {
         throw cacChannel::unsupportedByService();
     }
+    if ( INVALID_DB_REQ ( type ) ) {
+        throw cacChannel::badType ();
+    }
     comQueSendMsgMinder minder ( this->sendQue, guard );
     this->sendQue.insertRequestWithPayLoad ( CA_PROTO_WRITE_NOTIFY,  
         type, nElem, chan.getSID(guard), io.getId(), pValue,