diff --git a/query/src/main/java/org/apache/kylin/query/util/QueryUtil.java b/query/src/main/java/org/apache/kylin/query/util/QueryUtil.java
index 055289578a5..424a1725ac4 100644
--- a/query/src/main/java/org/apache/kylin/query/util/QueryUtil.java
+++ b/query/src/main/java/org/apache/kylin/query/util/QueryUtil.java
@@ -123,6 +123,9 @@ public static String makeErrorMsgUserFriendly(Throwable e) {
     }
 
     public static String makeErrorMsgUserFriendly(String errorMsg) {
+        if (errorMsg == null) {
+            return "Unknown error.";
+        }
         try {
             // make one line
             errorMsg = errorMsg.replaceAll("\\s", " ");
diff --git a/query/src/test/java/org/apache/kylin/query/util/QueryUtilTest.java b/query/src/test/java/org/apache/kylin/query/util/QueryUtilTest.java
index 4d766b9e33d..30f4934f386 100644
--- a/query/src/test/java/org/apache/kylin/query/util/QueryUtilTest.java
+++ b/query/src/test/java/org/apache/kylin/query/util/QueryUtilTest.java
@@ -225,4 +225,10 @@ public void testRemoveCommentInSql() {
             Assert.assertEquals(originSql, QueryUtil.removeCommentInSql(sqlWithComment));
         }
     }
+
+    @Test
+    public void testUnknownErrorResponseMessage() {
+        String msg = QueryUtil.makeErrorMsgUserFriendly(new NullPointerException());
+        Assert.assertEquals("Unknown error.", msg);
+    }
 }