diff --git a/src/ca/caProto.h b/src/ca/caProto.h
index 84190bf56..f61f52e08 100644
--- a/src/ca/caProto.h
+++ b/src/ca/caProto.h
@@ -41,6 +41,7 @@
 #   define CA_V410(MINOR) ((MINOR)>=10u)  /* beacon counter */
 #   define CA_V411(MINOR) ((MINOR)>=11u)  /* sequence numbers in UDP version command */
 #   define CA_V412(MINOR) ((MINOR)>=12u)  /* TCP-based search requests */
+#   define CA_V413(MINOR) ((MINOR)>=13u)  /* Allow zero length in requests. */
 #elif CA_MAJOR_PROTOCOL_REVISION > 4u
 #   define CA_V41(MINOR) ( 1u )
 #   define CA_V42(MINOR) ( 1u )
@@ -54,6 +55,7 @@
 #   define CA_V410(MINOR) ( 1u )
 #   define CA_V411(MINOR) ( 1u )
 #   define CA_V412(MINOR) ( 1u )
+#   define CA_V413(MINOR) ( 1u )
 #else
 #   define CA_V41(MINOR) ( 0u )
 #   define CA_V42(MINOR) ( 0u )
@@ -67,6 +69,7 @@
 #   define CA_V410(MINOR) ( 0u )
 #   define CA_V411(MINOR) ( 0u )
 #   define CA_V412(MINOR) ( 0u )
+#   define CA_V413(MINOR) ( 0u )
 #endif
 
 /*
diff --git a/src/ca/nciu.cpp b/src/ca/nciu.cpp
index f61172808..c5ae941b2 100644
--- a/src/ca/nciu.cpp
+++ b/src/ca/nciu.cpp
@@ -291,9 +291,6 @@ cacChannel::ioStatus nciu::read (
     if ( countIn > this->count ) {
         throw cacChannel::outOfBounds ();
     }
-    if ( countIn == 0 ) {
-        countIn = this->count;
-    }
 
     //
     // fail out if their arguments are invalid
diff --git a/src/ca/nciu.h b/src/ca/nciu.h
index 5660a8c85..de070dcea 100644
--- a/src/ca/nciu.h
+++ b/src/ca/nciu.h
@@ -41,7 +41,7 @@
 #   include "shareLib.h"
 #endif
 
-#define CA_MINOR_PROTOCOL_REVISION 12
+#define CA_MINOR_PROTOCOL_REVISION 13
 #include "caProto.h"
 
 #include "cacIO.h"
@@ -205,6 +205,7 @@ public:
     void disconnectAllIO ( 
         epicsGuard < epicsMutex > &, epicsGuard < epicsMutex > & );
     bool connected ( epicsGuard < epicsMutex > & ) const; 
+    unsigned getcount() const { return count; }
 
 private:
     tsDLList < class baseNMIU > eventq;
diff --git a/src/ca/netIO.h b/src/ca/netIO.h
index b694bc141..57273427a 100644
--- a/src/ca/netIO.h
+++ b/src/ca/netIO.h
@@ -83,7 +83,7 @@ public:
     void show ( 
         epicsGuard < epicsMutex > &, unsigned level ) const;
     arrayElementCount getCount (
-        epicsGuard < epicsMutex > & ) const;
+        epicsGuard < epicsMutex > &, bool allow_zero ) const;
     unsigned getType (
         epicsGuard < epicsMutex > & ) const;
     unsigned getMask (
@@ -242,11 +242,11 @@ inline netSubscription * netSubscription::factory (
 }
 
 inline arrayElementCount netSubscription::getCount (
-    epicsGuard < epicsMutex > & guard ) const // X aCC 361
+    epicsGuard < epicsMutex > & guard, bool allow_zero ) const // X aCC 361
 {
     //guard.assertIdenticalMutex ( this->mutex );
     arrayElementCount nativeCount = this->privateChanForIO.nativeElementCount ( guard );
-    if ( this->count == 0u || this->count > nativeCount ) {
+    if ( (this->count == 0u && !allow_zero) || this->count > nativeCount ) {
         return nativeCount;
     }
     else {
diff --git a/src/ca/oldChannelNotify.cpp b/src/ca/oldChannelNotify.cpp
index 48ddde124..8865f8d63 100644
--- a/src/ca/oldChannelNotify.cpp
+++ b/src/ca/oldChannelNotify.cpp
@@ -280,6 +280,9 @@ int epicsShareAPI ca_array_get ( chtype type,
         if ( type < 0 ) {
             return ECA_BADTYPE;
         }
+        if ( count == 0 )
+            return ECA_BADCOUNT;
+
         unsigned tmpType = static_cast < unsigned > ( type );
         epicsGuard < epicsMutex > guard ( pChan->cacCtx.mutexRef () );
         pChan->eliminateExcessiveSendBacklog ( guard );
diff --git a/src/ca/tcpiiu.cpp b/src/ca/tcpiiu.cpp
index 214b0687c..20e2abc3b 100644
--- a/src/ca/tcpiiu.cpp
+++ b/src/ca/tcpiiu.cpp
@@ -1464,6 +1464,8 @@ void tcpiiu::readNotifyRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
     if ( nElem > maxElem ) {
         throw cacChannel::msgBodyCacheTooSmall ();
     }
+    if (nElem == 0 && !CA_V413(this->minorProtocolVersion))
+       nElem = chan.getcount();
     comQueSendMsgMinder minder ( this->sendQue, guard );
     this->sendQue.insertRequestHeader ( 
         CA_PROTO_READ_NOTIFY, 0u, 
@@ -1559,7 +1561,8 @@ void tcpiiu::subscriptionRequest (
     if ( mask > 0xffff ) {
         throw cacChannel::badEventSelection ();
     }
-    arrayElementCount nElem = subscr.getCount ( guard );
+    arrayElementCount nElem = subscr.getCount (
+        guard, CA_V413(this->minorProtocolVersion) );
     arrayElementCount maxBytes;
     if ( CA_V49 ( this->minorProtocolVersion ) ) {
         maxBytes = this->cacRef.largeBufferSizeTCP ();
@@ -1605,7 +1608,8 @@ void tcpiiu::subscriptionUpdateRequest (
     if ( this->state != iiucs_connected ) {
         return;
     }
-    arrayElementCount nElem = subscr.getCount ( guard );
+    arrayElementCount nElem = subscr.getCount (
+        guard, CA_V413(this->minorProtocolVersion) );
     arrayElementCount maxBytes;
     if ( CA_V49 ( this->minorProtocolVersion ) ) {
         maxBytes = this->cacRef.largeBufferSizeTCP ();
@@ -1643,7 +1647,8 @@ void tcpiiu::subscriptionCancelRequest ( epicsGuard < epicsMutex > & guard, // X
     this->sendQue.insertRequestHeader ( 
         CA_PROTO_EVENT_CANCEL, 0u, 
         static_cast < ca_uint16_t > ( subscr.getType ( guard ) ), 
-        static_cast < ca_uint16_t > ( subscr.getCount ( guard ) ), 
+        static_cast < ca_uint16_t > ( subscr.getCount (
+            guard, CA_V413(this->minorProtocolVersion) ) ),
         chan.getSID(guard), subscr.getId(), 
         CA_V49 ( this->minorProtocolVersion ) );
     minder.commit ();