diff --git a/src/core_read.cpp b/src/core_read.cpp
--- a/src/core_read.cpp
+++ b/src/core_read.cpp
@@ -26,8 +26,8 @@
     static std::map<std::string, opcodetype> mapOpNames;
 
     if (mapOpNames.empty()) {
-        for (int op = 0; op <= OP_NOP10; op++) {
-            // Allow OP_RESERVED to get into mapOpNames
+        for (int op = 0; op <= MAX_DEFINED_OP_VALUE; op++) {
+            // ignore all "PUSHDATA" ops, but dont ignore OP_RESERVED
             if (op < OP_NOP && op != OP_RESERVED) {
                 continue;
             }
diff --git a/src/script/interpreter.h b/src/script/interpreter.h
--- a/src/script/interpreter.h
+++ b/src/script/interpreter.h
@@ -107,6 +107,10 @@
     // Do we accept signature using SIGHASH_FORKID
     //
     SCRIPT_ENABLE_SIGHASH_FORKID = (1U << 16),
+
+    // Enable new opcodes activated from 15 May 2018 HF
+    //
+    SCRIPT_ENABLE_OPCODES_MONOLITH = (1U << 17),
 };
 
 bool CheckSignatureEncoding(const std::vector<uint8_t> &vchSig, uint32_t flags,
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -312,6 +312,8 @@
     }
     int nOpCount = 0;
     bool fRequireMinimal = (flags & SCRIPT_VERIFY_MINIMALDATA) != 0;
+    bool fEnabledOpCodesMonolith =
+        (flags & SCRIPT_ENABLE_OPCODES_MONOLITH) != 0;
 
     try {
         while (pc < pend) {
@@ -332,7 +334,7 @@
                 return set_error(serror, SCRIPT_ERR_OP_COUNT);
             }
 
-            if (opcode == OP_CAT || opcode == OP_SUBSTR || opcode == OP_LEFT ||
+            if (opcode == OP_CAT || opcode == OP_SPLIT || opcode == OP_LEFT ||
                 opcode == OP_RIGHT || opcode == OP_INVERT || opcode == OP_AND ||
                 opcode == OP_OR || opcode == OP_XOR || opcode == OP_2MUL ||
                 opcode == OP_2DIV || opcode == OP_MUL || opcode == OP_DIV ||
diff --git a/src/script/script.h b/src/script/script.h
--- a/src/script/script.h
+++ b/src/script/script.h
@@ -102,7 +102,7 @@
 
     // splice ops
     OP_CAT = 0x7e,
-    OP_SUBSTR = 0x7f,
+    OP_SPLIT = 0x7f,
     OP_LEFT = 0x80,
     OP_RIGHT = 0x81,
     OP_SIZE = 0x82,
@@ -134,6 +134,8 @@
     OP_MOD = 0x97,
     OP_LSHIFT = 0x98,
     OP_RSHIFT = 0x99,
+    OP_BIN2NUM = 0xba,
+    OP_NUM2BIN = 0xbb,
 
     OP_BOOLAND = 0x9a,
     OP_BOOLOR = 0x9b,
@@ -184,6 +186,9 @@
     OP_INVALIDOPCODE = 0xff,
 };
 
+// the op_code with the maximum value out of all defined opcodes
+#define MAX_DEFINED_OP_VALUE OP_NUM2BIN
+
 const char *GetOpName(opcodetype opcode);
 
 class scriptnum_error : public std::runtime_error {
diff --git a/src/script/script.cpp b/src/script/script.cpp
--- a/src/script/script.cpp
+++ b/src/script/script.cpp
@@ -121,8 +121,8 @@
         // splice ops
         case OP_CAT:
             return "OP_CAT";
-        case OP_SUBSTR:
-            return "OP_SUBSTR";
+        case OP_SPLIT:
+            return "OP_SPLIT";
         case OP_LEFT:
             return "OP_LEFT";
         case OP_RIGHT:
@@ -179,6 +179,10 @@
             return "OP_LSHIFT";
         case OP_RSHIFT:
             return "OP_RSHIFT";
+        case OP_BIN2NUM:
+            return "OP_BIN2NUM";
+        case OP_NUM2BIN:
+            return "OP_NUM2BIN";
         case OP_BOOLAND:
             return "OP_BOOLAND";
         case OP_BOOLOR:
diff --git a/src/test/data/script_tests.json b/src/test/data/script_tests.json
--- a/src/test/data/script_tests.json
+++ b/src/test/data/script_tests.json
@@ -240,9 +240,9 @@
 ["0", "IF NOP10 ENDIF 1", "P2SH,STRICTENC,DISCOURAGE_UPGRADABLE_NOPS", "OK",
  "Discouraged NOPs are allowed if not executed"],
 
-["0", "IF 0xba ELSE 1 ENDIF", "P2SH,STRICTENC", "OK", "opcodes above NOP10 invalid if executed"],
-["0", "IF 0xbb ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
-["0", "IF 0xbc ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
+["0", "IF BIN2NUM ELSE 1 ENDIF", "P2SH,STRICTENC", "OK", "BIN2NUM invalid unless ENABLE_OPCODES_MONOLITH"],
+["0", "IF NUM2BIN ELSE 1 ENDIF", "P2SH,STRICTENC", "OK", "NUM2BIN invalid unless ENABLE_OPCODES_MONOLITH"],
+["0", "IF 0xbc ELSE 1 ENDIF", "P2SH,STRICTENC", "OK", "opcodes above MAX_VALID_OP_VALUE invalid if executed"],
 ["0", "IF 0xbd ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
 ["0", "IF 0xbe ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
 ["0", "IF 0xbf ELSE 1 ENDIF", "P2SH,STRICTENC", "OK"],
@@ -819,8 +819,8 @@
 
 ["'a' 'b'", "CAT", "P2SH,STRICTENC", "DISABLED_OPCODE", "CAT disabled"],
 ["'a' 'b' 0", "IF CAT ELSE 1 ENDIF", "P2SH,STRICTENC", "DISABLED_OPCODE", "CAT disabled"],
-["'abc' 1 1", "SUBSTR", "P2SH,STRICTENC", "DISABLED_OPCODE", "SUBSTR disabled"],
-["'abc' 1 1 0", "IF SUBSTR ELSE 1 ENDIF", "P2SH,STRICTENC", "DISABLED_OPCODE", "SUBSTR disabled"],
+["'abc' 1 1", "SPLIT", "P2SH,STRICTENC", "DISABLED_OPCODE", "SPLIT disabled"],
+["'abc' 1 1 0", "IF SPLIT ELSE 1 ENDIF", "P2SH,STRICTENC", "DISABLED_OPCODE", "SPLIT disabled"],
 ["'abc' 2 0", "IF LEFT ELSE 1 ENDIF", "P2SH,STRICTENC", "DISABLED_OPCODE", "LEFT disabled"],
 ["'abc' 2 0", "IF RIGHT ELSE 1 ENDIF", "P2SH,STRICTENC", "DISABLED_OPCODE", "RIGHT disabled"],
 
@@ -878,9 +878,9 @@
  "P2SH,DISCOURAGE_UPGRADABLE_NOPS", "DISCOURAGE_UPGRADABLE_NOPS", "Discouraged NOP10 in redeemScript"],
 
 ["0x50","1", "P2SH,STRICTENC", "BAD_OPCODE", "opcode 0x50 is reserved"],
-["1", "IF 0xba ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE", "opcodes above NOP10 invalid if executed"],
-["1", "IF 0xbb ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
-["1", "IF 0xbc ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
+["1", "IF BIN2NUM ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE", "BIN2NUM invalid unless ENABLE_OPCODES_MONOLITH"],
+["1", "IF NUM2BIN ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE", "NUM2BIN invalid unless ENABLE_OPCODES_MONOLITH"],
+["1", "IF 0xbc ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE", "opcodes above MAX_VALID_OP_VALUE invalid if executed"],
 ["1", "IF 0xbd ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
 ["1", "IF 0xbe ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
 ["1", "IF 0xbf ELSE 1 ENDIF", "P2SH,STRICTENC", "BAD_OPCODE"],
@@ -1001,7 +1001,9 @@
 ["1","RESERVED", "P2SH,STRICTENC", "BAD_OPCODE", "OP_RESERVED is reserved"],
 ["1","RESERVED1", "P2SH,STRICTENC", "BAD_OPCODE", "OP_RESERVED1 is reserved"],
 ["1","RESERVED2", "P2SH,STRICTENC", "BAD_OPCODE", "OP_RESERVED2 is reserved"],
-["1","0xba", "P2SH,STRICTENC", "BAD_OPCODE", "0xba == OP_NOP10 + 1"],
+["1","BIN2NUM", "P2SH,STRICTENC", "BAD_OPCODE", "BIN2NUM invalid unless ENABLE_OPCODES_MONOLITH"],
+["1","NUM2BIN", "P2SH,STRICTENC", "BAD_OPCODE", "BIN2NUM invalid unless ENABLE_OPCODES_MONOLITH"],
+["1","0xbc", "P2SH,STRICTENC", "BAD_OPCODE", "0xbc == MAX_VALID_OP_VALUE + 1"],
 
 ["2147483648", "1ADD 1", "P2SH,STRICTENC", "UNKNOWN_ERROR", "We cannot do math on 5-byte integers"],
 ["2147483648", "NEGATE 1", "P2SH,STRICTENC", "UNKNOWN_ERROR", "We cannot do math on 5-byte integers"],
diff --git a/src/test/scriptflags.cpp b/src/test/scriptflags.cpp
--- a/src/test/scriptflags.cpp
+++ b/src/test/scriptflags.cpp
@@ -32,6 +32,7 @@
      SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM},
     {"COMPRESSED_PUBKEYTYPE", SCRIPT_VERIFY_COMPRESSED_PUBKEYTYPE},
     {"SIGHASH_FORKID", SCRIPT_ENABLE_SIGHASH_FORKID},
+    {"ENABLE_OPCODES_MONOLITH", SCRIPT_ENABLE_OPCODES_MONOLITH},
 };
 
 uint32_t ParseScriptFlags(std::string strFlags) {
diff --git a/test/functional/test_framework/script.py b/test/functional/test_framework/script.py
--- a/test/functional/test_framework/script.py
+++ b/test/functional/test_framework/script.py
@@ -48,6 +48,7 @@
 
 
 class CScriptOp(int):
+
     """A single script opcode"""
     __slots__ = []
 
@@ -178,7 +179,7 @@
 
 # splice ops
 OP_CAT = CScriptOp(0x7e)
-OP_SUBSTR = CScriptOp(0x7f)
+OP_SPLIT = CScriptOp(0x7f)
 OP_LEFT = CScriptOp(0x80)
 OP_RIGHT = CScriptOp(0x81)
 OP_SIZE = CScriptOp(0x82)
@@ -210,6 +211,8 @@
 OP_MOD = CScriptOp(0x97)
 OP_LSHIFT = CScriptOp(0x98)
 OP_RSHIFT = CScriptOp(0x99)
+OP_BIN2NUM = CScriptOp(0xba)
+OP_NUM2BIN = CScriptOp(0xbb)
 
 OP_BOOLAND = CScriptOp(0x9a)
 OP_BOOLOR = CScriptOp(0x9b)
@@ -309,7 +312,7 @@
     OP_TUCK,
 
     OP_CAT,
-    OP_SUBSTR,
+    OP_SPLIT,
     OP_LEFT,
     OP_RIGHT,
     OP_SIZE,
@@ -339,6 +342,8 @@
     OP_MOD,
     OP_LSHIFT,
     OP_RSHIFT,
+    OP_BIN2NUM,
+    OP_NUM2BIN,
 
     OP_BOOLAND,
     OP_BOOLOR,
@@ -435,7 +440,7 @@
     OP_SWAP: 'OP_SWAP',
     OP_TUCK: 'OP_TUCK',
     OP_CAT: 'OP_CAT',
-    OP_SUBSTR: 'OP_SUBSTR',
+    OP_SPLIT: 'OP_SPLIT',
     OP_LEFT: 'OP_LEFT',
     OP_RIGHT: 'OP_RIGHT',
     OP_SIZE: 'OP_SIZE',
@@ -462,6 +467,8 @@
     OP_MOD: 'OP_MOD',
     OP_LSHIFT: 'OP_LSHIFT',
     OP_RSHIFT: 'OP_RSHIFT',
+    OP_BIN2NUM: 'OP_BIN2NUM',
+    OP_NUM2BIN: 'OP_NUM2BIN',
     OP_BOOLAND: 'OP_BOOLAND',
     OP_BOOLOR: 'OP_BOOLOR',
     OP_NUMEQUAL: 'OP_NUMEQUAL',
@@ -554,7 +561,7 @@
     'OP_SWAP': OP_SWAP,
     'OP_TUCK': OP_TUCK,
     'OP_CAT': OP_CAT,
-    'OP_SUBSTR': OP_SUBSTR,
+    'OP_SPLIT': OP_SPLIT,
     'OP_LEFT': OP_LEFT,
     'OP_RIGHT': OP_RIGHT,
     'OP_SIZE': OP_SIZE,
@@ -581,6 +588,8 @@
     'OP_MOD': OP_MOD,
     'OP_LSHIFT': OP_LSHIFT,
     'OP_RSHIFT': OP_RSHIFT,
+    'OP_BIN2NUM': OP_BIN2NUM,
+    'OP_NUM2BIN': OP_NUM2BIN,
     'OP_BOOLAND': OP_BOOLAND,
     'OP_BOOLOR': OP_BOOLOR,
     'OP_NUMEQUAL': OP_NUMEQUAL,
@@ -621,11 +630,13 @@
 
 
 class CScriptInvalidError(Exception):
+
     """Base class for CScript exceptions"""
     pass
 
 
 class CScriptTruncatedPushDataError(CScriptInvalidError):
+
     """Invalid pushdata due to truncation"""
 
     def __init__(self, msg, data):
@@ -636,6 +647,7 @@
 
 
 class CScriptNum():
+
     def __init__(self, d=0):
         self.value = d
 
@@ -657,6 +669,7 @@
 
 
 class CScript(bytes):
+
     """Serialized script
 
     A bytes subclass, so you can use this directly whenever bytes are accepted.