diff --git a/CHANGES.txt b/CHANGES.txt
index 0f1ae93a18..3c19f1036c 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -92,6 +92,7 @@ Merged from 2.0:
  * Avoid costly range calculations for range queries on system keyspaces
    (CASSANDRA-6906)
  * Fix SSTable not released if stream session fails (CASSANDRA-6818)
+ * Avoid build failure due to ANTLR timeout (CASSANDRA-6991)
 Merged from 1.2:
  * Add UNLOGGED, COUNTER options to BATCH documentation (CASSANDRA-6816)
  * add extra SSL cipher suites (CASSANDRA-6613)
diff --git a/build.xml b/build.xml
index 5a42fc7e65..d2b892e0c5 100644
--- a/build.xml
+++ b/build.xml
@@ -230,6 +230,8 @@
             classpath="${build.lib}/antlr-3.2.jar"
             fork="true"
             failonerror="true">
+         <arg value="-Xconversiontimeout" />
+         <arg value="10000" />
          <arg value="${build.src.java}/org/apache/cassandra/cql3/Cql.g" />
          <arg value="-fo" />
          <arg value="${build.src.gen-java}/org/apache/cassandra/cql3/" />