diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala
index b1064de8e9db5..844673f66d103 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala
@@ -925,8 +925,8 @@ private[hive] object HiveQl {
     case Token("TOK_FUNCTION", Token(CASE(), Nil) :: branches) =>
       val transformed = branches.drop(1).sliding(2, 2).map {
         case Seq(condVal, value) =>
-          // FIXME: the key will get evaluated for multiple times in CaseWhen's eval(). Hence
-          // effectful / non-deterministic key expressions are *not* supported at the moment.
+          // FIXME (SPARK-2155): the key will get evaluated for multiple times in CaseWhen's eval().
+          // Hence effectful / non-deterministic key expressions are *not* supported at the moment.
           // We should consider adding new Expressions to get around this.
           Seq(Equals(nodeToExpr(branches(0)), nodeToExpr(condVal)),
               nodeToExpr(value))