diff --git a/servers/zms/src/main/java/com/yahoo/athenz/zms/ZMSImpl.java b/servers/zms/src/main/java/com/yahoo/athenz/zms/ZMSImpl.java
index ece08bfa9e7..9b0906b453a 100644
--- a/servers/zms/src/main/java/com/yahoo/athenz/zms/ZMSImpl.java
+++ b/servers/zms/src/main/java/com/yahoo/athenz/zms/ZMSImpl.java
@@ -3998,9 +3998,13 @@ long getModTimestamp(String matchingTag) {
         matchingTag = removeQuotes(matchingTag);
 
         if (LOG.isDebugEnabled()) {
-            LOG.debug("getModTimestamp: matching tag (" + matchingTag + ")");
+            LOG.debug("getModTimestamp: matching tag ({})", matchingTag);
         }
-        
+
+        if (matchingTag.isEmpty()) {
+            return timestamp;
+        }
+
         try {
             Timestamp tagStamp = Timestamp.fromString(matchingTag);
             if (tagStamp == null) {
@@ -4009,7 +4013,8 @@ long getModTimestamp(String matchingTag) {
             timestamp = tagStamp.millis();
         } catch (IllegalArgumentException exc) {
             if (LOG.isWarnEnabled()) {
-                LOG.warn("getModTimestamp: matching tag(" + matchingTag + ") has bad format. Return -1L by default.");
+                LOG.warn("getModTimestamp: matching tag({}) has bad format. Return 0 by default.",
+                        matchingTag);
             }
         }
         
diff --git a/servers/zms/src/test/java/com/yahoo/athenz/zms/ZMSImplTest.java b/servers/zms/src/test/java/com/yahoo/athenz/zms/ZMSImplTest.java
index 6721124eb5c..924d12213a7 100644
--- a/servers/zms/src/test/java/com/yahoo/athenz/zms/ZMSImplTest.java
+++ b/servers/zms/src/test/java/com/yahoo/athenz/zms/ZMSImplTest.java
@@ -14373,5 +14373,13 @@ public void testValidateString() {
             assertEquals(ex.getCode(), 400);
         }
     }
+
+    @Test
+    public void testgetModTimestampEmtpy() {
+        ZMSImpl zmsImpl = zmsInit();
+        assertEquals(zmsImpl.getModTimestamp(null), 0);
+        assertEquals(zmsImpl.getModTimestamp("\"\""), 0);
+        assertEquals(zmsImpl.getModTimestamp(""), 0);
+    }
 }