diff --git a/core/src/main/java/org/elasticsearch/common/regex/Regex.java b/core/src/main/java/org/elasticsearch/common/regex/Regex.java
index f5c3094e31d..061ad6c26c0 100644
--- a/core/src/main/java/org/elasticsearch/common/regex/Regex.java
+++ b/core/src/main/java/org/elasticsearch/common/regex/Regex.java
@@ -150,7 +150,7 @@ public class Regex {
                 pFlags |= Pattern.LITERAL;
             } else if ("COMMENTS".equals(s)) {
                 pFlags |= Pattern.COMMENTS;
-            } else if ("UNICODE_CHAR_CLASS".equals(s)) {
+            } else if (("UNICODE_CHAR_CLASS".equals(s)) || ("UNICODE_CHARACTER_CLASS".equals(s))) {
                 pFlags |= UNICODE_CHARACTER_CLASS;
             } else {
                 throw new IllegalArgumentException("Unknown regex flag [" + s + "]");
diff --git a/core/src/test/java/org/elasticsearch/common/regex/RegexTests.java b/core/src/test/java/org/elasticsearch/common/regex/RegexTests.java
index ee0756f28ce..85c2be77af5 100644
--- a/core/src/test/java/org/elasticsearch/common/regex/RegexTests.java
+++ b/core/src/test/java/org/elasticsearch/common/regex/RegexTests.java
@@ -28,7 +28,7 @@ import static org.hamcrest.Matchers.equalTo;
 public class RegexTests extends ESTestCase {
     public void testFlags() {
         String[] supportedFlags = new String[]{"CASE_INSENSITIVE", "MULTILINE", "DOTALL", "UNICODE_CASE", "CANON_EQ", "UNIX_LINES",
-                "LITERAL", "COMMENTS", "UNICODE_CHAR_CLASS"};
+                "LITERAL", "COMMENTS", "UNICODE_CHAR_CLASS", "UNICODE_CHARACTER_CLASS"};
         int[] flags = new int[]{Pattern.CASE_INSENSITIVE, Pattern.MULTILINE, Pattern.DOTALL, Pattern.UNICODE_CASE, Pattern.CANON_EQ,
                 Pattern.UNIX_LINES, Pattern.LITERAL, Pattern.COMMENTS, Regex.UNICODE_CHARACTER_CLASS};
         Random random = getRandom();