diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index a6f8fd0e1..e86bf4fc1 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -428,6 +428,10 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, un
 
 				case OP_COUNT_ACKS:
 				{
+					if (SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS) {
+                                           return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS);
+                                       }
+
 
 					// (secondary_chain_id ack_period liveness_period -- )
 					if (stack.size() < 3)