diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 7755c1d..2f9c120 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -8,3 +8,11 @@ repos:
     rev: e2c2116d86a80e72e7146a06e68b7c228afc6319
     hooks:
       - id: cmake-format
+  - repo: local
+    hooks:
+      - id: debug verbose check
+        name: disallow checking in DEBUG_VERBOSE=1
+        description: disallow checking in DEBUG_VERBOSE=1
+        entry: '^#define DEBUG_VERBOSE 1$'
+        language: pygrep
+        types: [c++]
\ No newline at end of file
diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index d50033b..8c52643 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -543,6 +543,27 @@ Node *&getOrCreateChild(Node *&self, uint8_t index) {
   }
 }
 
+void fixMaxVersion(Node *self) {
+  for (;;) {
+    int64_t result = std::numeric_limits<int64_t>::lowest();
+    if (self->entryPresent) {
+      result = std::max(result, self->entry.pointVersion);
+      result = std::max(result, self->entry.rangeVersion);
+    }
+    for (int i = getChildGeq(self, 0); i >= 0; i = getChildGeq(self, i + 1)) {
+      result = std::max(result, getChildExists(self, i)->maxVersion);
+    }
+    if (self->maxVersion == result) {
+      break;
+    }
+    self->maxVersion = result;
+    if (self->parent == nullptr) {
+      break;
+    }
+    self = self->parent;
+  }
+}
+
 // Precondition - an entry for index must exist in the node
 void eraseChild(Node *self, uint8_t index) {
   free(getChildExists(self, index));
@@ -814,21 +835,6 @@ void destroyTree(Node *root) {
   }
 }
 
-void invalidateMax(Node *self) {
-  int64_t expectedMax = std::numeric_limits<int64_t>::lowest();
-  if (self->entryPresent) {
-    expectedMax = std::max(expectedMax, self->entry.pointVersion);
-    expectedMax = std::max(expectedMax, self->entry.rangeVersion);
-  }
-  for (int i = getChildGeq(self, 0); i >= 0; i = getChildGeq(self, i + 1)) {
-    expectedMax = std::max(expectedMax, getChildExists(self, i)->maxVersion);
-  }
-  self->maxVersion = expectedMax;
-  if (self->parent != nullptr) {
-    invalidateMax(self->parent);
-  }
-}
-
 struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
   void check(const ReadRange *reads, Result *result, int count) const {
     for (int i = 0; i < count; ++i) {
@@ -858,33 +864,54 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
     for (int i = 0; i < count; ++i) {
       const auto &w = writes[i];
       if (w.end.len > 0) {
-        auto *n = insert(&root, std::span<const uint8_t>(w.end.p, w.end.len),
-                         std::numeric_limits<int64_t>::lowest());
-        if (!n->entryPresent) {
-          auto *p = prevLogical(n);
-          assert(p != nullptr);
-          n->entryPresent = true;
-          n->entry.pointVersion = p->entry.rangeVersion;
-          n->entry.rangeVersion = p->entry.rangeVersion;
+        auto *begin =
+            insert(&root, std::span<const uint8_t>(w.begin.p, w.begin.len),
+                   w.writeVersion);
+
+        const bool insertedBegin = !std::exchange(begin->entryPresent, true);
+        begin->entry.pointVersion = w.writeVersion;
+
+        auto *end = insert(&root, std::span<const uint8_t>(w.end.p, w.end.len),
+                           std::numeric_limits<int64_t>::lowest());
+
+        const bool insertedEnd = !std::exchange(end->entryPresent, true);
+        if (insertedEnd) {
+          // begin may have been invalidated
+          auto iter =
+              lastLeq(root, std::span<const uint8_t>(w.begin.p, w.begin.len));
+          assert(iter.cmp == 0);
+          begin = iter.n;
         }
 
-        auto *end = n;
-        n = insert(&root, std::span<const uint8_t>(w.begin.p, w.begin.len),
-                   std::numeric_limits<int64_t>::lowest());
-        auto *begin = n;
-        n->entryPresent = true;
-        n->entry.pointVersion = w.writeVersion;
-        n->entry.rangeVersion = w.writeVersion;
-        for (n = nextLogical(n); n != end;) {
-          auto *old = n;
-          n = nextLogical(n);
+        if (insertedBegin) {
+          auto *p = prevLogical(begin);
+          assert(p != nullptr);
+          begin->entry.rangeVersion = p->entry.rangeVersion;
+        }
+
+        if (insertedEnd) {
+          auto *p = prevLogical(end);
+          assert(p != nullptr);
+          end->entryPresent = true;
+          end->entry.pointVersion = p->entry.rangeVersion;
+          end->entry.rangeVersion = p->entry.rangeVersion;
+        }
+
+        begin->entry.rangeVersion = w.writeVersion;
+
+        for (begin = nextLogical(begin); begin != end;) {
+          auto *old = begin;
+          begin = nextLogical(begin);
           old->entryPresent = false;
+          fixMaxVersion(old);
           if (old->numChildren == 0 && old->parent != nullptr) {
             eraseChild(old->parent, old->parentsIndex);
           }
         }
-        invalidateMax(begin);
-        invalidateMax(end);
+
+        if (insertedEnd) {
+          fixMaxVersion(end);
+        }
       } else {
         auto *n =
             insert(&root, std::span<const uint8_t>(w.begin.p, w.begin.len),
@@ -1175,6 +1202,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
       fflush(stdout);
       abort();
     }
+#if DEBUG_VERBOSE && !defined(NDEBUG)
+    fprintf(stderr, "Check correctness\n");
+#endif
     bool success = checkCorrectness(driver.cs.root, driver.refImpl);
     if (!success) {
       debugPrintDot(stdout, driver.cs.root);