diff --git a/src/ripple/app/ledger/impl/LedgerConsensusImp.cpp b/src/ripple/app/ledger/impl/LedgerConsensusImp.cpp
index e251e8f18..73468a33e 100644
--- a/src/ripple/app/ledger/impl/LedgerConsensusImp.cpp
+++ b/src/ripple/app/ledger/impl/LedgerConsensusImp.cpp
@@ -981,11 +981,13 @@ void LedgerConsensusImp::accept (std::shared_ptr<SHAMap> set)
         auto buildLCL = std::make_shared<Ledger>(
             *mPreviousLedger,
             app_.timeKeeper().closeTime());
-        auto constexpr v2_ledger_seq_switch = 40'000'000;
-        if (buildLCL->info().seq > v2_ledger_seq_switch &&
-           !buildLCL->stateMap().is_v2())
+        auto const v2_enabled = buildLCL->rules().enabled(featureSHAMapV2,
+                                                       app_.config().features);
+        auto v2_transition = false;
+        if (v2_enabled && !buildLCL->stateMap().is_v2())
         {
             buildLCL->make_v2();
+            v2_transition = true;
         }
 
         // Set up to write SHAMap changes to our database,
@@ -1022,15 +1024,10 @@ void LedgerConsensusImp::accept (std::shared_ptr<SHAMap> set)
 
         buildLCL->updateSkipList ();
 
-        // unshare in case a nodestore load changed the
-        // version back, otherwise the map is inconsistent
-        if (buildLCL->info().seq > v2_ledger_seq_switch &&
-            !buildLCL->stateMap().is_v2())
         {
-            buildLCL->unshare();
-        }
+            // Write the final version of all modified SHAMap
+            // nodes to the node store to preserve the new LCL
 
-        {
             int asf = buildLCL->stateMap().flushDirty (
                 hotACCOUNT_NODE, buildLCL->info().seq);
             int tmf = buildLCL->txMap().flushDirty (
@@ -1039,6 +1036,7 @@ void LedgerConsensusImp::accept (std::shared_ptr<SHAMap> set)
                 asf << " accounts and " <<
                 tmf << " transaction nodes";
         }
+        buildLCL->unshare();
 
         // Accept ledger
         buildLCL->setAccepted(closeTime, mCloseResolution,
diff --git a/src/ripple/app/main/Application.cpp b/src/ripple/app/main/Application.cpp
index e1d6be53a..d61eececf 100644
--- a/src/ripple/app/main/Application.cpp
+++ b/src/ripple/app/main/Application.cpp
@@ -1006,7 +1006,7 @@ bool ApplicationImp::setup()
         enabledAmendments.append (detail::preEnabledAmendments ());
 
         m_amendmentTable = make_AmendmentTable (
-            weeks(2),
+            weeks{2},
             MAJORITY_FRACTION,
             supportedAmendments,
             enabledAmendments,
diff --git a/src/ripple/protocol/Feature.h b/src/ripple/protocol/Feature.h
index 8b867f7a4..33ec8ef5b 100644
--- a/src/ripple/protocol/Feature.h
+++ b/src/ripple/protocol/Feature.h
@@ -42,6 +42,7 @@ extern uint256 const featureFeeEscalation;
 extern uint256 const featureFlowV2;
 extern uint256 const featureOwnerPaysFee;
 extern uint256 const featureCompareFlowV1V2;
+extern uint256 const featureSHAMapV2;
 
 } // ripple
 
diff --git a/src/ripple/protocol/impl/Feature.cpp b/src/ripple/protocol/impl/Feature.cpp
index cd1b1f510..b43e9edf6 100644
--- a/src/ripple/protocol/impl/Feature.cpp
+++ b/src/ripple/protocol/impl/Feature.cpp
@@ -53,5 +53,6 @@ uint256 const featureFeeEscalation = feature("FeeEscalation");
 uint256 const featureFlowV2 = feature("FlowV2");
 uint256 const featureOwnerPaysFee = feature("OwnerPaysFee");
 uint256 const featureCompareFlowV1V2 = feature("CompareFlowV1V2");
+uint256 const featureSHAMapV2 = feature("SHAMapV2");
 
 } // ripple
diff --git a/src/ripple/shamap/SHAMap.h b/src/ripple/shamap/SHAMap.h
index 75af96c3b..e8578c1f7 100644
--- a/src/ripple/shamap/SHAMap.h
+++ b/src/ripple/shamap/SHAMap.h
@@ -315,6 +315,7 @@ private:
                      std::shared_ptr<SHAMapItem const> const& otherMapItem,
                      bool isFirstMap, Delta & differences, int & maxCount) const;
     int walkSubTree (bool doWrite, NodeObjectType t, std::uint32_t seq);
+    bool isInconsistentNode(std::shared_ptr<SHAMapAbstractNode> const& node) const;
 };
 
 inline
diff --git a/src/ripple/shamap/SHAMapTreeNode.h b/src/ripple/shamap/SHAMapTreeNode.h
index c9e15afe2..ad31ca839 100644
--- a/src/ripple/shamap/SHAMapTreeNode.h
+++ b/src/ripple/shamap/SHAMapTreeNode.h
@@ -166,7 +166,7 @@ public:
     void shareChild (int m, std::shared_ptr<SHAMapAbstractNode> const& child);
     SHAMapAbstractNode* getChildPointer (int branch);
     std::shared_ptr<SHAMapAbstractNode> getChild (int branch);
-    std::shared_ptr<SHAMapAbstractNode>
+    virtual std::shared_ptr<SHAMapAbstractNode>
         canonicalizeChild (int branch, std::shared_ptr<SHAMapAbstractNode> node);
 
     // sync functions
@@ -212,6 +212,8 @@ public:
     uint256 const& key() const override;
     void setChildren(std::shared_ptr<SHAMapTreeNode> const& child1,
                      std::shared_ptr<SHAMapTreeNode> const& child2);
+    std::shared_ptr<SHAMapAbstractNode>
+        canonicalizeChild (int branch, std::shared_ptr<SHAMapAbstractNode> node) override;
     void invariants(bool is_v2, bool is_root = false) const override;
 
     friend std::shared_ptr<SHAMapAbstractNode>
diff --git a/src/ripple/shamap/impl/SHAMap.cpp b/src/ripple/shamap/impl/SHAMap.cpp
index 1000dd6c3..4a50bccc9 100644
--- a/src/ripple/shamap/impl/SHAMap.cpp
+++ b/src/ripple/shamap/impl/SHAMap.cpp
@@ -207,7 +207,8 @@ SHAMap::walkTowardsKey(uint256 const& id, SharedPtrNodeStack* stack) const
             if (inNode->isInner())
             {
                 auto n = std::dynamic_pointer_cast<SHAMapInnerNodeV2>(inNode);
-                assert(n);
+                if (n == nullptr)
+                    return nullptr;
                 nodeID = SHAMapNodeID{n->depth(), n->common()};
             }
             else
@@ -255,6 +256,11 @@ SHAMap::fetchNodeFromDB (SHAMapHash const& hash) const
                     {
                         auto root =  std::dynamic_pointer_cast<SHAMapInnerNode>(root_);
                         assert(root);
+if (!root->isEmpty())
+{
+    std::cerr << "isv2 = " << isv2 << '\n';
+    std::cerr << "is_v2() = " << is_v2() << '\n';
+}
                         assert(root->isEmpty());
                         if (isv2)
                         {
@@ -405,7 +411,7 @@ SHAMapAbstractNode* SHAMap::descend (SHAMapInnerNode* parent, int branch) const
         return ret;
 
     std::shared_ptr<SHAMapAbstractNode> node = fetchNodeNT (parent->getChildHash (branch));
-    if (!node)
+    if (!node || isInconsistentNode(node))
         return nullptr;
 
     node = parent->canonicalizeChild (branch, std::move(node));
@@ -420,7 +426,7 @@ SHAMap::descend (std::shared_ptr<SHAMapInnerNode> const& parent, int branch) con
         return node;
 
     node = fetchNode (parent->getChildHash (branch));
-    if (!node)
+    if (!node || isInconsistentNode(node))
         return nullptr;
 
     node = parent->canonicalizeChild (branch, std::move(node));
@@ -452,6 +458,8 @@ SHAMap::descend (SHAMapInnerNode * parent, SHAMapNodeID const& parentID,
     if (!child)
     {
         std::shared_ptr<SHAMapAbstractNode> childNode = fetchNodeNT (childHash, filter);
+        if (isInconsistentNode(childNode))
+            childNode = nullptr;
 
         if (childNode)
         {
@@ -518,6 +526,8 @@ SHAMap::descendAsync (SHAMapInnerNode* parent, int branch,
         }
     }
 
+    if (isInconsistentNode(ptr))
+        ptr = nullptr;
     if (ptr)
         ptr = parent->canonicalizeChild (branch, std::move(ptr));
 
@@ -561,7 +571,8 @@ SHAMap::firstBelow(std::shared_ptr<SHAMapAbstractNode> node,
     {
         if (is_v2())
         {
-            auto inner2 = std::static_pointer_cast<SHAMapInnerNodeV2>(inner);
+            auto inner2 = std::dynamic_pointer_cast<SHAMapInnerNodeV2>(inner);
+            assert(inner2 != nullptr);
             stack.push({inner2, {inner2->depth(), inner2->common()}});
         }
         else
@@ -1373,7 +1384,20 @@ SHAMap::invariants() const
     auto node = root_.get();
     assert(node != nullptr);
     assert(!node->isLeaf());
+    SharedPtrNodeStack stack;
+    for (auto leaf = peekFirstItem(stack); leaf != nullptr;
+         leaf = peekNextItem(leaf->peekItem()->key(), stack))
+        ;
     node->invariants(is_v2(), true);
 }
 
+bool
+SHAMap::isInconsistentNode(std::shared_ptr<SHAMapAbstractNode> const& node) const
+{
+    if (std::dynamic_pointer_cast<SHAMapTreeNode>(node) != nullptr)
+        return false;
+    bool is_node_v2 = std::dynamic_pointer_cast<SHAMapInnerNodeV2>(node) != nullptr;
+    return is_v2() != is_node_v2;
+}
+
 } // ripple
diff --git a/src/ripple/shamap/impl/SHAMapSync.cpp b/src/ripple/shamap/impl/SHAMapSync.cpp
index e15b0d7c4..b7c73d813 100644
--- a/src/ripple/shamap/impl/SHAMapSync.cpp
+++ b/src/ripple/shamap/impl/SHAMapSync.cpp
@@ -262,7 +262,7 @@ SHAMap::getMissingNodes(std::size_t max, SHAMapSyncFilter* filter)
             auto const& nodeHash = parent->getChildHash (branch);
 
             auto nodePtr = fetchNodeNT(nodeHash, filter);
-            if (nodePtr)
+            if (nodePtr && !isInconsistentNode(nodePtr))
             {
                 ++hits;
                 if (backed_)
@@ -523,15 +523,18 @@ SHAMap::addKnownNode (const SHAMapNodeID& node, Blob const& rawNode,
                 return SHAMapAddNode::useful ();
             }
 
-#ifndef NDEBUG
-            if (newNode && newNode->isInner())
+            if (newNode && isInconsistentNode(newNode))
             {
-                bool isv2 = std::dynamic_pointer_cast<SHAMapInnerNodeV2>(newNode) != nullptr;
-                assert(isv2 == is_v2());
+                return SHAMapAddNode::invalid();
             }
-#endif
+
             if (backed_)
+            {
+                auto temp = newNode;
                 canonicalize (childHash, newNode);
+                if (isInconsistentNode(newNode))
+                    newNode = temp;
+            }
             newNode = prevNode->canonicalizeChild (branch, std::move(newNode));
 
             if (filter)
diff --git a/src/ripple/shamap/impl/SHAMapTreeNode.cpp b/src/ripple/shamap/impl/SHAMapTreeNode.cpp
index e14140115..e456073d3 100644
--- a/src/ripple/shamap/impl/SHAMapTreeNode.cpp
+++ b/src/ripple/shamap/impl/SHAMapTreeNode.cpp
@@ -710,6 +710,33 @@ SHAMapInnerNode::canonicalizeChild(int branch, std::shared_ptr<SHAMapAbstractNod
     else
     {
         // Hook this node up
+        // node must not be a v2 inner node
+        assert(std::dynamic_pointer_cast<SHAMapInnerNodeV2>(node) == nullptr);
+        mChildren[branch] = node;
+    }
+    return node;
+}
+
+std::shared_ptr<SHAMapAbstractNode>
+SHAMapInnerNodeV2::canonicalizeChild(int branch, std::shared_ptr<SHAMapAbstractNode> node)
+{
+    assert (branch >= 0 && branch < 16);
+    assert (isInner());
+    assert (node);
+    assert (node->getNodeHash() == mHashes[branch]);
+
+    std::unique_lock <std::mutex> lock (childLock);
+    if (mChildren[branch])
+    {
+        // There is already a node hooked up, return it
+        node = mChildren[branch];
+    }
+    else
+    {
+        // Hook this node up
+        // node must not be a v1 inner node
+        assert(std::dynamic_pointer_cast<SHAMapInnerNodeV2>(node) != nullptr ||
+               std::dynamic_pointer_cast<SHAMapTreeNode>(node)    != nullptr);
         mChildren[branch] = node;
     }
     return node;