diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index a87a11d6..1348a0f3 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -205,7 +205,7 @@ bool CheckBlockIndex(int &txBlockIndex, int blockIndex)
         if (blockDelta > 0)
             return false;
         // blockDelta must be greater than 100 but lesser than 262144
-        if ((blockDelta > -101) || (blockDelta < -262144))
+        if ((blockDelta > -101) || (blockDelta < -262144) && (blockDelta != 0))
             return false;
         // check if txBlockIndex refers to an actual block
         if (txBlockIndex > blockIndex)
@@ -417,10 +417,23 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
                     break;
                 }
 
-#ifdef BITCOIN_TX // zen-tx can't process OP_CHECKBLOCKATHEIGHT because it requires an active chain
+#ifndef BITCOIN_ZCASHCONSENSUS_H // zen-tx can't process OP_CHECKBLOCKATHEIGHT because it requires an active chain
                 case OP_CHECKBLOCKATHEIGHT:
                 {
-                    return set_error(serror, SCRIPT_ERR_CHECKBLOCKATHEIGHT_UNVERIFIED);
+                    // we need two objects on the stack
+                    if (stack.size() < 2)
+                        return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
+
+                    valtype vchBlockHash(stacktop(-2));
+                    valtype vchBlockIndex(stacktop(-1));
+
+                    if ((vchBlockIndex.size() > sizeof(int)) || (vchBlockHash.size() > 32))
+                        return set_error(serror, SCRIPT_ERR_CHECKBLOCKATHEIGHT);
+
+                    // since we can't access chain data then we treat OP_CHECKBLOCKATHEIGHT as a NOP
+                    popstack(stack);
+                    popstack(stack);
+                    stack.push_back(vchTrue);
                 }
                 break;
 #else
diff --git a/src/script/standard.cpp b/src/script/standard.cpp
index f9e4649e..24544b0f 100644
--- a/src/script/standard.cpp
+++ b/src/script/standard.cpp
@@ -12,7 +12,9 @@
 
 #include <boost/foreach.hpp>
 
+#if defined(BITCOIN_ZCASHCONSENSUS_H)
 #include "main.h"
+#endif
 
 using namespace std;
 
@@ -307,7 +309,7 @@ public:
         return false;
     }
 
-#ifdef BITCOIN_TX // zen-tx does not have access to chain state so no replay protection is possible
+#ifndef BITCOIN_ZCASHCONSENSUS_H // zen-tx does not have access to chain state so no replay protection is possible
     bool operator()(const CKeyID &keyID) const {
         script->clear();
         *script << OP_DUP << OP_HASH160 << ToByteVector(keyID) << OP_EQUALVERIFY << OP_CHECKSIG;