diff --git a/base-hlc/src/main/java/org/apache/bifromq/basehlc/HLC.java b/base-hlc/src/main/java/org/apache/bifromq/basehlc/HLC.java
index 82d29a1ff..b90d7621d 100644
--- a/base-hlc/src/main/java/org/apache/bifromq/basehlc/HLC.java
+++ b/base-hlc/src/main/java/org/apache/bifromq/basehlc/HLC.java
@@ -118,7 +118,7 @@ public long update(long otherHLC) {
                 c = Math.max(c, otherC) + 1;
             } else if (updateL == l) {
                 c++;
-            } else if (otherL == l) {
+            } else if (updateL == otherL) {
                 c = otherC + 1;
             } else {
                 c = 0;
diff --git a/base-hlc/src/test/java/org/apache/bifromq/basehlc/HLCTest.java b/base-hlc/src/test/java/org/apache/bifromq/basehlc/HLCTest.java
index 7acdfbb84..15c85bad3 100644
--- a/base-hlc/src/test/java/org/apache/bifromq/basehlc/HLCTest.java
+++ b/base-hlc/src/test/java/org/apache/bifromq/basehlc/HLCTest.java
@@ -47,4 +47,13 @@ public void update() {
             t1 = t;
         }
     }
+
+    @Test
+    public void updateWithFutureTimestampPreservesCausality() {
+        long observed = ((System.currentTimeMillis() + 1000) << 16) | 5;
+
+        long updated = HLC.INST.update(observed);
+
+        assertTrue(updated > observed);
+    }
 }