diff --git a/hadoop-hdds/config/src/main/java/org/apache/hadoop/hdds/conf/TimeDurationUtil.java b/hadoop-hdds/config/src/main/java/org/apache/hadoop/hdds/conf/TimeDurationUtil.java
index 12c495393276..fa2b7328b7dd 100644
--- a/hadoop-hdds/config/src/main/java/org/apache/hadoop/hdds/conf/TimeDurationUtil.java
+++ b/hadoop-hdds/config/src/main/java/org/apache/hadoop/hdds/conf/TimeDurationUtil.java
@@ -50,6 +50,9 @@ public static long getTimeDurationHelper(String name, String vStr,
     if (null == vUnit) {
       LOG.warn("No unit for " + name + "(" + vStr + ") assuming " + unit);
       vUnit = ParsedTimeDuration.unitFor(unit);
+      if (null == vUnit) {
+        throw new IllegalArgumentException("Unexpected unit: " + unit);
+      }
     } else {
       vStr = vStr.substring(0, vStr.lastIndexOf(vUnit.suffix()));
     }