diff --git a/src/consensus/tx_verify.h b/src/consensus/tx_verify.h
--- a/src/consensus/tx_verify.h
+++ b/src/consensus/tx_verify.h
@@ -18,10 +18,8 @@
  * Context-independent validity checks for coinbase and non-coinbase
  * transactions.
  */
-bool CheckRegularTransaction(const CTransaction &tx, CValidationState &state,
-                             bool fCheckDuplicateInputs = true);
-bool CheckCoinbase(const CTransaction &tx, CValidationState &state,
-                   bool fCheckDuplicateInputs = true);
+bool CheckRegularTransaction(const CTransaction &tx, CValidationState &state);
+bool CheckCoinbase(const CTransaction &tx, CValidationState &state);
 
 namespace Consensus {
 
diff --git a/src/consensus/tx_verify.cpp b/src/consensus/tx_verify.cpp
--- a/src/consensus/tx_verify.cpp
+++ b/src/consensus/tx_verify.cpp
@@ -186,8 +186,7 @@
 }
 
 static bool CheckTransactionCommon(const CTransaction &tx,
-                                   CValidationState &state,
-                                   bool fCheckDuplicateInputs) {
+                                   CValidationState &state) {
     // Basic checks that don't depend on any context
     if (tx.vin.empty()) {
         return state.DoS(10, false, REJECT_INVALID, "bad-txns-vin-empty");
@@ -227,29 +226,16 @@
         return state.DoS(100, false, REJECT_INVALID, "bad-txn-sigops");
     }
 
-    // Check for duplicate inputs - note that this check is slow so we skip it
-    // in CheckBlock
-    if (fCheckDuplicateInputs) {
-        std::set<COutPoint> vInOutPoints;
-        for (const auto &txin : tx.vin) {
-            if (!vInOutPoints.insert(txin.prevout).second) {
-                return state.DoS(100, false, REJECT_INVALID,
-                                 "bad-txns-inputs-duplicate");
-            }
-        }
-    }
-
     return true;
 }
 
-bool CheckCoinbase(const CTransaction &tx, CValidationState &state,
-                   bool fCheckDuplicateInputs) {
+bool CheckCoinbase(const CTransaction &tx, CValidationState &state) {
     if (!tx.IsCoinBase()) {
         return state.DoS(100, false, REJECT_INVALID, "bad-cb-missing", false,
                          "first tx is not coinbase");
     }
 
-    if (!CheckTransactionCommon(tx, state, fCheckDuplicateInputs)) {
+    if (!CheckTransactionCommon(tx, state)) {
         // CheckTransactionCommon fill in the state.
         return false;
     }
@@ -262,22 +248,27 @@
     return true;
 }
 
-bool CheckRegularTransaction(const CTransaction &tx, CValidationState &state,
-                             bool fCheckDuplicateInputs) {
+bool CheckRegularTransaction(const CTransaction &tx, CValidationState &state) {
     if (tx.IsCoinBase()) {
         return state.DoS(100, false, REJECT_INVALID, "bad-tx-coinbase");
     }
 
-    if (!CheckTransactionCommon(tx, state, fCheckDuplicateInputs)) {
+    if (!CheckTransactionCommon(tx, state)) {
         // CheckTransactionCommon fill in the state.
         return false;
     }
 
+    std::unordered_set<COutPoint, SaltedOutpointHasher> vInOutPoints;
     for (const auto &txin : tx.vin) {
         if (txin.prevout.IsNull()) {
             return state.DoS(10, false, REJECT_INVALID,
                              "bad-txns-prevout-null");
         }
+
+        if (!vInOutPoints.insert(txin.prevout).second) {
+            return state.DoS(100, false, REJECT_INVALID,
+                             "bad-txns-inputs-duplicate");
+        }
     }
 
     return true;
diff --git a/src/test/sigopcount_tests.cpp b/src/test/sigopcount_tests.cpp
--- a/src/test/sigopcount_tests.cpp
+++ b/src/test/sigopcount_tests.cpp
@@ -253,7 +253,7 @@
 
     {
         CValidationState state;
-        BOOST_CHECK(CheckRegularTransaction(CTransaction(tx), state, false));
+        BOOST_CHECK(CheckRegularTransaction(CTransaction(tx), state));
     }
 
     // Get just before the limit.
@@ -263,7 +263,7 @@
 
     {
         CValidationState state;
-        BOOST_CHECK(CheckRegularTransaction(CTransaction(tx), state, false));
+        BOOST_CHECK(CheckRegularTransaction(CTransaction(tx), state));
     }
 
     // And go over.
@@ -271,7 +271,7 @@
 
     {
         CValidationState state;
-        BOOST_CHECK(!CheckRegularTransaction(CTransaction(tx), state, false));
+        BOOST_CHECK(!CheckRegularTransaction(CTransaction(tx), state));
         BOOST_CHECK_EQUAL(state.GetRejectReason(), "bad-txn-sigops");
     }
 }
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -386,7 +386,7 @@
     }
 
     // Coinbase is only valid in a block, not as a loose transaction.
-    if (!CheckRegularTransaction(tx, state, true)) {
+    if (!CheckRegularTransaction(tx, state)) {
         // state filled in by CheckRegularTransaction.
         return false;
     }
@@ -3079,7 +3079,7 @@
     }
 
     // And a valid coinbase.
-    if (!CheckCoinbase(*block.vtx[0], state, false)) {
+    if (!CheckCoinbase(*block.vtx[0], state)) {
         return state.Invalid(false, state.GetRejectCode(),
                              state.GetRejectReason(),
                              strprintf("Coinbase check failed (txid %s) %s",
@@ -3113,11 +3113,11 @@
             break;
         }
 
-        // Check that the transaction is valid. because this check differs for
-        // the coinbase, the loos is arranged such as this only runs after at
+        // Check that the transaction is valid. Because this check differs for
+        // the coinbase, the loop is arranged such as this only runs after at
         // least one increment.
         tx = block.vtx[i].get();
-        if (!CheckRegularTransaction(*tx, state, false)) {
+        if (!CheckRegularTransaction(*tx, state)) {
             return state.Invalid(
                 false, state.GetRejectCode(), state.GetRejectReason(),
                 strprintf("Transaction check failed (txid %s) %s",