diff --git a/src/validation.h b/src/validation.h
--- a/src/validation.h
+++ b/src/validation.h
@@ -709,10 +709,6 @@
 static const unsigned int REJECT_INTERNAL = 0x100;
 /** Too high fee. Can not be triggered by P2P transactions */
 static const unsigned int REJECT_HIGHFEE = 0x100;
-/** Transaction is already known (either in mempool or blockchain) */
-static const unsigned int REJECT_ALREADY_KNOWN = 0x101;
-/** Transaction conflicts with a transaction already known */
-static const unsigned int REJECT_CONFLICT = 0x102;
 /** Block conflicts with a transaction already known */
 static const unsigned int REJECT_AGAINST_FINALIZED = 0x103;
 
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -507,8 +507,7 @@
 
     // Is it already in the memory pool?
     if (pool.exists(txid)) {
-        return state.Invalid(false, REJECT_ALREADY_KNOWN,
-                             "txn-already-in-mempool");
+        return state.Invalid(false, REJECT_DUPLICATE, "txn-already-in-mempool");
     }
 
     // Check for conflicts with in-memory transactions
@@ -516,7 +515,7 @@
         auto itConflicting = pool.mapNextTx.find(txin.prevout);
         if (itConflicting != pool.mapNextTx.end()) {
             // Disable replacement feature for good
-            return state.Invalid(false, REJECT_CONFLICT,
+            return state.Invalid(false, REJECT_DUPLICATE,
                                  "txn-mempool-conflict");
         }
     }