diff --git a/src/chainparams.cpp b/src/chainparams.cpp
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -83,6 +83,9 @@
     CMainParams() {
         strNetworkID = "main";
         consensus.nSubsidyHalvingInterval = 210000;
+        // 00000000000000ce80a7e057163a4db1d5ad7b20fb6f598c9597b9665c8fb0d4 -
+        // April 1, 2012
+        consensus.BIP16Height = 173805;
         consensus.BIP34Height = 227931;
         consensus.BIP34Hash = uint256S(
             "000000000000024b89b42a942fe0d9fea3bb44ab7bd1b19115dd6a759c0808b8");
@@ -249,6 +252,8 @@
     CTestNetParams() {
         strNetworkID = "test";
         consensus.nSubsidyHalvingInterval = 210000;
+        // 00000000040b4e986385315e14bee30ad876d8b47f748025b26683116d21aa65
+        consensus.BIP16Height = 514;
         consensus.BIP34Height = 21111;
         consensus.BIP34Hash = uint256S(
             "0000000023b3a96d3484e5abb3755c413e7d41500f8e2a5c3f0dd01299cd8ef8");
@@ -368,6 +373,8 @@
     CRegTestParams() {
         strNetworkID = "regtest";
         consensus.nSubsidyHalvingInterval = 150;
+        // always enforce P2SH BIP16 on regtest
+        consensus.BIP16Height = 0;
         // BIP34 has not activated on regtest (far in the future so block v1 are
         // not rejected in tests)
         consensus.BIP34Height = 100000000;
diff --git a/src/consensus/consensus.h b/src/consensus/consensus.h
--- a/src/consensus/consensus.h
+++ b/src/consensus/consensus.h
@@ -32,8 +32,6 @@
 static const int COINBASE_MATURITY = 100;
 /** Coinbase scripts have their own script size limit. */
 static const int MAX_COINBASE_SCRIPTSIG_SIZE = 100;
-/** Activation time for P2SH (April 1st 2012) */
-static const int64_t P2SH_ACTIVATION_TIME = 1333234914;
 
 /** Flags for nSequence and nLockTime locks */
 /** Interpret sequence numbers as relative lock-time constraints. */
diff --git a/src/consensus/params.h b/src/consensus/params.h
--- a/src/consensus/params.h
+++ b/src/consensus/params.h
@@ -19,6 +19,8 @@
 struct Params {
     uint256 hashGenesisBlock;
     int nSubsidyHalvingInterval;
+    /** Block height at which BIP16 becomes active */
+    int BIP16Height;
     /** Block height and hash at which BIP34 becomes active */
     int BIP34Height;
     uint256 BIP34Hash;
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -436,44 +436,6 @@
         std::runtime_error);
     g_mempool.clear();
 
-    // Invalid (pre-p2sh) txn in mempool, template creation fails.
-    std::array<int64_t, CBlockIndex::nMedianTimeSpan> times;
-    for (int i = 0; i < CBlockIndex::nMedianTimeSpan; i++) {
-        // Trick the MedianTimePast.
-        times[i] = chainActive.Tip()
-                       ->GetAncestor(chainActive.Tip()->nHeight - i)
-                       ->nTime;
-        chainActive.Tip()->GetAncestor(chainActive.Tip()->nHeight - i)->nTime =
-            P2SH_ACTIVATION_TIME;
-    }
-
-    tx.vin[0].prevout = COutPoint(txFirst[0]->GetId(), 0);
-    tx.vin[0].scriptSig = CScript() << OP_1;
-    tx.vout[0].nValue = BLOCKSUBSIDY - LOWFEE;
-    script = CScript() << OP_0;
-    tx.vout[0].scriptPubKey = GetScriptForDestination(CScriptID(script));
-    hash = tx.GetId();
-    g_mempool.addUnchecked(
-        hash,
-        entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(true).FromTx(tx));
-    tx.vin[0].prevout = COutPoint(hash, 0);
-    tx.vin[0].scriptSig = CScript()
-                          << std::vector<uint8_t>(script.begin(), script.end());
-    tx.vout[0].nValue -= LOWFEE;
-    hash = tx.GetId();
-    g_mempool.addUnchecked(
-        hash,
-        entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(false).FromTx(tx));
-    BOOST_CHECK_THROW(
-        BlockAssembler(config, g_mempool).CreateNewBlock(scriptPubKey),
-        std::runtime_error);
-    g_mempool.clear();
-    for (int i = 0; i < CBlockIndex::nMedianTimeSpan; i++) {
-        // Restore the MedianTimePast.
-        chainActive.Tip()->GetAncestor(chainActive.Tip()->nHeight - i)->nTime =
-            times[i];
-    }
-
     // Double spend txn pair in mempool, template creation fails.
     tx.vin[0].prevout = COutPoint(txFirst[0]->GetId(), 0);
     tx.vin[0].scriptSig = CScript() << OP_1;
@@ -523,6 +485,30 @@
     BOOST_CHECK(
         pblocktemplate =
             BlockAssembler(config, g_mempool).CreateNewBlock(scriptPubKey));
+
+    // Invalid p2sh txn in mempool, template creation fails
+    tx.vin[0].prevout = COutPoint(txFirst[0]->GetId(), 0);
+    tx.vin[0].scriptSig = CScript() << OP_1;
+    tx.vout[0].nValue = BLOCKSUBSIDY - LOWFEE;
+    script = CScript() << OP_0;
+    tx.vout[0].scriptPubKey = GetScriptForDestination(CScriptID(script));
+    hash = tx.GetId();
+    g_mempool.addUnchecked(
+        hash,
+        entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(true).FromTx(tx));
+    tx.vin[0].prevout = COutPoint(hash, 0);
+    tx.vin[0].scriptSig = CScript()
+                          << std::vector<uint8_t>(script.begin(), script.end());
+    tx.vout[0].nValue -= LOWFEE;
+    hash = tx.GetId();
+    g_mempool.addUnchecked(
+        hash,
+        entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(false).FromTx(tx));
+    BOOST_CHECK_THROW(
+        BlockAssembler(config, g_mempool).CreateNewBlock(scriptPubKey),
+        std::runtime_error);
+    g_mempool.clear();
+
     // Delete the dummy blocks again.
     while (chainActive.Tip()->nHeight > nHeight) {
         CBlockIndex *del = chainActive.Tip();
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1557,8 +1557,8 @@
 
     uint32_t flags = SCRIPT_VERIFY_NONE;
 
-    // P2SH didn't become active until Apr 1 2012
-    if (pindex->GetMedianTimePast() >= P2SH_ACTIVATION_TIME) {
+    // Start enforcing P2SH (BIP16)
+    if ((pindex->nHeight + 1) >= consensusParams.BIP16Height) {
         flags |= SCRIPT_VERIFY_P2SH;
     }