diff --git a/server/src/main/java/org/elasticsearch/index/query/BoolQueryBuilder.java b/server/src/main/java/org/elasticsearch/index/query/BoolQueryBuilder.java
index fa4e5eba99ac7..d932df81f3398 100644
--- a/server/src/main/java/org/elasticsearch/index/query/BoolQueryBuilder.java
+++ b/server/src/main/java/org/elasticsearch/index/query/BoolQueryBuilder.java
@@ -52,8 +52,8 @@ public class BoolQueryBuilder extends AbstractQueryBuilder<BoolQueryBuilder> {
 
     public static final boolean ADJUST_PURE_NEGATIVE_DEFAULT = true;
 
-    private static final ParseField MUSTNOT = new ParseField("mustNot");    // TODO deprecate?
-    private static final ParseField MUST_NOT = new ParseField("must_not");
+    private static final ParseField MUST_NOT = new ParseField("must_not")
+        .withDeprecation("mustNot");
     private static final ParseField FILTER = new ParseField("filter");
     private static final ParseField SHOULD = new ParseField("should");
     private static final ParseField MUST = new ParseField("must");
@@ -279,8 +279,6 @@ private static void doXArrayContent(ParseField field, List<QueryBuilder> clauses
             SHOULD);
         PARSER.declareObjectArray((builder, clauses) -> clauses.forEach(builder::mustNot), (p, c) -> parseInnerQueryBuilder(p),
             MUST_NOT);
-        PARSER.declareObjectArray((builder, clauses) -> clauses.forEach(builder::mustNot), (p, c) -> parseInnerQueryBuilder(p),
-            MUSTNOT);   // TODO should we deprecate this version?
         PARSER.declareObjectArray((builder, clauses) -> clauses.forEach(builder::filter), (p, c) -> parseInnerQueryBuilder(p),
             FILTER);
         PARSER.declareBoolean(BoolQueryBuilder::adjustPureNegative, ADJUST_PURE_NEGATIVE);
diff --git a/server/src/test/java/org/elasticsearch/index/query/BoolQueryBuilderTests.java b/server/src/test/java/org/elasticsearch/index/query/BoolQueryBuilderTests.java
index c974f106e56f8..93d46ed592570 100644
--- a/server/src/test/java/org/elasticsearch/index/query/BoolQueryBuilderTests.java
+++ b/server/src/test/java/org/elasticsearch/index/query/BoolQueryBuilderTests.java
@@ -137,7 +137,7 @@ protected Map<String, BoolQueryBuilder> getAlternateVersions() {
         }
         if (tempQueryBuilder.mustNot().size() > 0) {
             QueryBuilder mustNot = tempQueryBuilder.mustNot().get(0);
-            contentString += (randomBoolean() ? "\"must_not\": " : "\"mustNot\": ") + mustNot.toString() + ",";
+            contentString += "\"must_not\":" + mustNot.toString() + ",";
             expectedQuery.mustNot(mustNot);
         }
         if (tempQueryBuilder.should().size() > 0) {
@@ -297,6 +297,14 @@ public void testUnknownQueryName() throws IOException {
 
     }
 
+    public void testDeprecation() throws IOException {
+        String query = "{\"bool\" : {\"mustNot\" : { \"match_all\" : { } } } }";
+        QueryBuilder q = parseQuery(query);
+        QueryBuilder expected = new BoolQueryBuilder().mustNot(new MatchAllQueryBuilder());
+        assertEquals(expected, q);
+        assertWarnings("Deprecated field [mustNot] used, expected [must_not] instead");
+    }
+
     public void testRewrite() throws IOException {
         BoolQueryBuilder boolQueryBuilder = new BoolQueryBuilder();
         boolean mustRewrite = false;