diff --git a/src/main.cpp b/src/main.cpp
index 8f58547fe..47138aefe 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1685,6 +1685,11 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
 
     unsigned int flags = fStrictPayToScriptHash ? SCRIPT_VERIFY_P2SH : SCRIPT_VERIFY_NONE;
 
+    // Start enforcing the DERSIG (BIP66) rules, for block.nVersion=3 blocks, when 75% of the network has upgraded:
+    if (block.nVersion >= 3 && CBlockIndex::IsSuperMajority(3, pindex->pprev, Params().EnforceBlockUpgradeMajority())) {
+        flags |= SCRIPT_VERIFY_DERSIG;
+    }
+
     CBlockUndo blockundo;
 
     CCheckQueueControl<CScriptCheck> control(fScriptChecks && nScriptCheckThreads ? &scriptcheckqueue : NULL);
@@ -2524,6 +2529,13 @@ bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationState& sta
                              REJECT_OBSOLETE, "bad-version");
     }
 
+    // Reject block.nVersion=2 blocks when 95% (75% on testnet) of the network has upgraded:
+    if (block.nVersion < 3 && CBlockIndex::IsSuperMajority(3, pindexPrev, Params().RejectBlockOutdatedMajority()))
+    {
+        return state.Invalid(error("%s : rejected nVersion=2 block", __func__),
+                             REJECT_OBSOLETE, "bad-version");
+    }
+
     return true;
 }
 
diff --git a/src/primitives/block.h b/src/primitives/block.h
index a18959253..9c17902e1 100644
--- a/src/primitives/block.h
+++ b/src/primitives/block.h
@@ -24,7 +24,7 @@ class CBlockHeader
 {
 public:
     // header
-    static const int32_t CURRENT_VERSION=2;
+    static const int32_t CURRENT_VERSION=3;
     int32_t nVersion;
     uint256 hashPrevBlock;
     uint256 hashMerkleRoot;
diff --git a/src/script/bitcoinconsensus.h b/src/script/bitcoinconsensus.h
index 15e3337a8..c57d8b3cc 100644
--- a/src/script/bitcoinconsensus.h
+++ b/src/script/bitcoinconsensus.h
@@ -46,6 +46,7 @@ enum
 {
     bitcoinconsensus_SCRIPT_FLAGS_VERIFY_NONE      = 0,
     bitcoinconsensus_SCRIPT_FLAGS_VERIFY_P2SH      = (1U << 0), // evaluate P2SH (BIP16) subscripts
+    bitcoinconsensus_SCRIPT_FLAGS_VERIFY_DERSIG    = (1U << 2), // enforce strict DER (BIP66) compliance
 };
 
 /// Returns 1 if the input nIn of the serialized transaction pointed to by
diff --git a/src/script/standard.h b/src/script/standard.h
index c4b82b4c4..3fea6b9ab 100644
--- a/src/script/standard.h
+++ b/src/script/standard.h
@@ -45,6 +45,7 @@ static const unsigned int MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH;
  * blocks and we must accept those blocks.
  */
 static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
+                                                         SCRIPT_VERIFY_DERSIG |
                                                          SCRIPT_VERIFY_STRICTENC |
                                                          SCRIPT_VERIFY_MINIMALDATA |
                                                          SCRIPT_VERIFY_NULLDUMMY |