diff --git a/CHANGES.txt b/CHANGES.txt
index 0eb7ed5f7e..2fc6e48a94 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,5 @@
 4.0.15
+ * Change the resolution of AbstractCommitLogService#lastSyncedAt to nanos to be aligned with later comparisons (CASSANDRA-20074)
  * Backport of CASSANDRA-17812: Rate-limit new client connection auth setup to avoid overwhelming bcrypt (CASSANDRA-20057)
  * Support UDTs and vectors as clustering keys in descending order (CASSANDRA-20050)
  * Fix CQL in snapshot's schema which did not contained UDTs used as reverse clustering columns (CASSANDRA-20036)
diff --git a/src/java/org/apache/cassandra/db/commitlog/AbstractCommitLogService.java b/src/java/org/apache/cassandra/db/commitlog/AbstractCommitLogService.java
index a65ef00a11..8b3acdae5e 100644
--- a/src/java/org/apache/cassandra/db/commitlog/AbstractCommitLogService.java
+++ b/src/java/org/apache/cassandra/db/commitlog/AbstractCommitLogService.java
@@ -45,7 +45,7 @@ public abstract class AbstractCommitLogService
     private volatile boolean shutdown = false;
 
     // all Allocations written before this time will be synced
-    protected volatile long lastSyncedAt = System.currentTimeMillis();
+    protected volatile long lastSyncedAt = MonotonicClock.preciseTime.now();
 
     // counts of total written, and pending, log messages
     private final AtomicLong written = new AtomicLong(0);