diff --git a/VersionedMap.cpp b/VersionedMap.cpp
index 9eb3866..9946c7f 100644
--- a/VersionedMap.cpp
+++ b/VersionedMap.cpp
@@ -111,10 +111,20 @@ struct Entry {
 
   Entry *addref() const {
     ++refCount;
+#if DEBUG_VERBOSE
+    if (debugVerboseEnabled) {
+      printf("addref %p to %d\n", this, refCount);
+    }
+#endif
     return (Entry *)this;
   }
 
   void delref() const {
+#if DEBUG_VERBOSE
+    if (debugVerboseEnabled) {
+      printf("delref %p to %d\n", this, refCount - 1);
+    }
+#endif
     if (--refCount == 0) {
       free((void *)this);
     }
@@ -165,7 +175,8 @@ constexpr uint32_t kUpsizeNodes = kUpsizeBytes / sizeof(Node);
 static_assert(kUpsizeNodes * sizeof(Node) == kUpsizeBytes);
 
 struct BitSet {
-  explicit BitSet(uint32_t size) : words((uint64_t *)malloc(size / 8 + 8)) {}
+  explicit BitSet(uint32_t size)
+      : words((uint64_t *)calloc(size / 64 + 1, 8)) {}
 
   bool test(uint32_t i) const {
     return words[i >> 6] & (uint64_t(1) << (i & 63));
@@ -250,6 +261,14 @@ struct MemManager {
   }
 
   void gc(const uint32_t *roots, int numRoots, int64_t oldestVersion) {
+#if DEBUG_VERBOSE
+    if (debugVerboseEnabled) {
+      printf("GC roots:\n");
+      for (int i = 0; i < numRoots; ++i) {
+        printf("  %u\n", roots[i]);
+      }
+    }
+#endif
     // Calculate reachable set
     BitSet reachable{next};
     // Each node has at most 3 children and nodes along the search path aren't
@@ -257,7 +276,17 @@ struct MemManager {
     uint32_t stack[2 * kPathLengthUpperBound];
     int stackIndex = 0;
     auto tryPush = [&](uint32_t p) {
+#if DEBUG_VERBOSE
+      if (debugVerboseEnabled) {
+        printf("  GC: visit: %u\n", p);
+      }
+#endif
       if (!reachable.set(p)) {
+#if DEBUG_VERBOSE
+        if (debugVerboseEnabled) {
+          printf("  GC: push on to stack: %u\n", p);
+        }
+#endif
         assert(stackIndex < sizeof(stack) / sizeof(stack[0]));
         stack[stackIndex++] = p;
       }
@@ -279,7 +308,9 @@ struct MemManager {
               tryPush(node.pointer[node.replacedPointer]);
             }
           }
-          tryPush(node.pointer[2]);
+          if (node.pointer[2] != 0) {
+            tryPush(node.pointer[2]);
+          }
         } else {
           if (node.pointer[0] != 0) {
             tryPush(node.pointer[0]);
@@ -480,6 +511,11 @@ struct VersionedMap::Impl {
 
     auto doCopy = [&]() {
       uint32_t copy = mm.allocate();
+#if DEBUG_VERBOSE
+      if (debugVerboseEnabled) {
+        printf("Copy %u to %u\n", node, copy);
+      }
+#endif
       auto &c = mm.base[copy];
       c.entry = n.entry->addref();
       c.pointer[which] = child;
@@ -860,6 +896,11 @@ VersionedMap::Iterator::operator=(Iterator &&other) noexcept {
 
 VersionedMap::Iterator::VersionedMutation
 VersionedMap::Iterator::operator*() const {
+#if DEBUG_VERBOSE
+  if (debugVerboseEnabled) {
+    printf("Dereference %u\n", impl->finger.backNode());
+  }
+#endif
   assert(impl->finger.searchPathSize() != 0);
   assert(impl->mutationIndex < impl->mutationCount);
   assert(impl->mutationIndex >= 0);
@@ -1100,6 +1141,10 @@ int64_t VersionedMap::getVersion() const { return impl->latestVersion; }
 
 int64_t VersionedMap::getOldestVersion() const { return impl->oldestVersion; }
 
+void VersionedMap::setOldestVersion(int64_t oldestVersion) {
+  impl->setOldestVersion(oldestVersion);
+}
+
 // TODO implement getBytes
 
 // ==================== END IMPLEMENTATION ====================
@@ -1122,6 +1167,7 @@ void VersionedMap::Impl::printInOrderHelper(int64_t version, uint32_t node,
   for (int i = 0; i < depth; ++i) {
     printf("  ");
   }
+  printf("node %u: ", node);
   printf("%.*s", mm.base[node].entry->keyLen, mm.base[node].entry->getKey());
   if (mm.base[node].entry->valLen >= 0) {
     printf(" -> '%.*s' @ %" PRId64, mm.base[node].entry->valLen,
@@ -1181,11 +1227,10 @@ int main() {
     }
     const int64_t v = 3;
     cast(versionedMap)->printInOrder(v);
-    weaselab::VersionedMap::Key k = {(const uint8_t *)"a", 1};
+    weaselab::VersionedMap::Key k = {(const uint8_t *)"a", 2};
     weaselab::VersionedMap::Iterator iter;
     versionedMap.firstGeq(&k, &v, &iter, 1);
-    auto begin = versionedMap.begin(v);
-    assert(iter == begin);
+    versionedMap.setOldestVersion(2);
     breakpoint_me();
     for (auto end = versionedMap.end(v); iter != end; ++iter) {
       const auto &m = *iter;