diff --git a/CHANGES.txt b/CHANGES.txt
index f8e024181a..22efd72eff 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -83,6 +83,25 @@ Merged from 5.0:
  * Deprecate and ignore use_deterministic_table_id (CASSANDRA-19809)
  * Prioritize built indexes in IndexStatusManager (CASSANDRA-19400)
  * Add java.base/java.lang.reflect among opens for jvm11-client.options (CASSANDRA-19780)
+Merged from 4.1:
+Merged from 4.0:
+ * Fix memory leak in BTree.FastBuilder (CASSANDRA-19785)
+ * Fix millisecond and microsecond precision for commit log replay (CASSANDRA-19448)
+ * Improve accuracy of memtable heap usage tracking (CASSANDRA-17298)
+ * Fix rendering UNSET collection types in query tracing (CASSANDRA-19880)
+ * Fix latency reported by ideal consistency level monitoring (CASSANDRA-19651)
+ * Do not spam log with SSLExceptions (CASSANDRA-18839)
+
+5.0.0
+5.0-rc2
+ * Fix direct IO support always being evaluated to false upon the first start of a node (CASSANDRA-19779)
+ * Memtable allocation type unslabbed_heap_buffers_logged will cause an assertion error for TrieMemtables and SegmentedTrieMemtables (CASSANDRA-19835)
+Merged from 4.0:
+ * Use default commitlog settings in test YAMLs (CASSANDRA-19830)
+
+
+5.0-rc1
+>>>>>>> cassandra-5.0
  * Move bcpkix-jdk18on to build dependencies, update to 1.78 and explicitly enumerate transitive dependencies (CASSANDRA-19739)
  * Avoid streams in the common case for UpdateTransaction creation (CASSANDRA-19675)
  * Only wait until native_transport_timeout for dispatcher to finish (CASSANDRA-19697)
@@ -131,6 +150,24 @@ Merged from 4.1:
  * Refresh stale paxos commit (CASSANDRA-19617)
  * Reduce info logging from automatic paxos repair (CASSANDRA-19445)
  * Support legacy plain_text_auth section in credentials file removed unintentionally (CASSANDRA-19498)
+Merged from 4.0:
+ * Fix millisecond and microsecond precision for commit log replay (CASSANDRA-19448)
+ * Improve accuracy of memtable heap usage tracking (CASSANDRA-17298)
+ * Fix rendering UNSET collection types in query tracing (CASSANDRA-19880)
+ * Fix latency reported by ideal consistency level monitoring (CASSANDRA-19651)
+ * Use default commitlog settings in test YAMLs (CASSANDRA-19830)
+ * Do not spam log with SSLExceptions (CASSANDRA-18839)
+ * Fix schema.cql created by a snapshot after dropping more than one column (CASSANDRA-19747)
+ * UnsupportedOperationException when reducing scope for LCS compactions (CASSANDRA-19704)
+ * Make LWT conditions behavior on frozen and non-frozen columns consistent for null column values (CASSANDRA-19637)
+ * Add timeout specifically for bootstrapping nodes (CASSANDRA-15439)
+ * Bring Redhat packge dirs/ownership/perms in line with Debian package (CASSANDRA-19565)
+Merged from 3.0:
+ * Upgrade OWASP to 10.0.0 (CASSANDRA-19738)
+
+
+4.1.5
+>>>>>>> cassandra-4.1
  * Make queries visible to the "system_views.queries" virtual table at the coordinator level (CASSANDRA-19577)
  * Fix hints delivery for a node going down repeatedly (CASSANDRA-19495)
  * Do not go to disk for reading hints file sizes (CASSANDRA-19477)
diff --git a/src/java/org/apache/cassandra/utils/btree/BTree.java b/src/java/org/apache/cassandra/utils/btree/BTree.java
index 7377ca129f..2ac80df48e 100644
--- a/src/java/org/apache/cassandra/utils/btree/BTree.java
+++ b/src/java/org/apache/cassandra/utils/btree/BTree.java
@@ -3317,28 +3317,52 @@ public class BTree
         public void close()
         {
             reset();
-            pool.offer(this);
-            pool = null;
+            if (pool != null)
+            {
+                pool.offer(this);
+                pool = null;
+            }
         }
 
         @Override
         void reset()
         {
-            // we clear precisely to leaf().count and branch.count because, in the case of a builder,
-            // if we ever fill the buffer we will consume it entirely for the tree we are building
-            // so the last count should match the number of non-null entries
-            Arrays.fill(leaf().buffer, 0, leaf().count, null);
+            Arrays.fill(leaf().buffer, null);
             leaf().count = 0;
             BranchBuilder branch = leaf().parent;
             while (branch != null && branch.inUse)
             {
-                Arrays.fill(branch.buffer, 0, branch.count, null);
-                Arrays.fill(branch.buffer, MAX_KEYS, MAX_KEYS + 1 + branch.count, null);
+                Arrays.fill(branch.buffer, null);
                 branch.count = 0;
                 branch.inUse = false;
                 branch = branch.parent;
             }
         }
+
+        public boolean validateEmpty()
+        {
+            LeafOrBranchBuilder cur = leaf();
+            boolean hasOnlyNulls = true;
+            while (hasOnlyNulls && cur != null)
+            {
+                hasOnlyNulls = hasOnlyNulls(cur.buffer) && hasOnlyNulls(cur.savedBuffer) && cur.savedNextKey == null;
+                cur = cur.parent;
+            }
+            return hasOnlyNulls;
+        }
+
+        private static boolean hasOnlyNulls(Object[] buffer)
+        {
+            if (buffer == null)
+                return true;
+
+            for (int i = 0 ; i < buffer.length ; ++i)
+            {
+                if (buffer[i] != null)
+                    return false;
+            }
+            return true;
+        }
     }
 
     private static abstract class AbstractUpdater extends AbstractFastBuilder implements AutoCloseable
diff --git a/test/burn/org/apache/cassandra/utils/LongBTreeTest.java b/test/burn/org/apache/cassandra/utils/LongBTreeTest.java
index 9aa13f9467..d8a4f81637 100644
--- a/test/burn/org/apache/cassandra/utils/LongBTreeTest.java
+++ b/test/burn/org/apache/cassandra/utils/LongBTreeTest.java
@@ -730,6 +730,9 @@ public class LongBTreeTest
                 Object[] btree = builder.build();
                 assertEquals(i + 1, BTree.size(btree));
                 assertTrue(""+i, BTree.<Integer>isWellFormed(btree, naturalOrder()));
+                assertTrue(""+i, BTree.<Integer>isWellFormed(btree, naturalOrder()));
+                builder.close();
+                assertTrue(builder.validateEmpty());
             }
         }
     }