diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala
index 226eead5c67e8..f22507b8c21e1 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala
@@ -205,6 +205,12 @@ private[sql] abstract class SparkStrategies extends QueryPlanner[SparkPlan] {
     def apply(plan: LogicalPlan): Seq[SparkPlan] = plan match {
       case logical.Aggregate(groupingExpressions, resultExpressions, child)
         if sqlContext.conf.useSqlAggregate2 =>
+        // 0. Make sure we can convert.
+        resultExpressions.foreach {
+          case agg1: AggregateExpression =>
+            sys.error(s"$agg1 is not supported. Please set spark.sql.useAggregate2 to false.")
+          case _ => // ok
+        }
         // 1. Extracts all distinct aggregate expressions from the resultExpressions.
         val aggregateExpressions = resultExpressions.flatMap { expr =>
           expr.collect {
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveContext.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveContext.scala
index 4146038a44383..0b0fbeb7340b9 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveContext.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveContext.scala
@@ -21,6 +21,8 @@ import java.io.File
 import java.net.{URL, URLClassLoader}
 import java.sql.Timestamp
 
+import org.apache.spark.sql.execution.aggregate2.ConvertAggregateFunction
+
 import scala.collection.JavaConversions._
 import scala.collection.mutable.HashMap
 import scala.language.implicitConversions
@@ -385,6 +387,7 @@ class HiveContext(sc: SparkContext) extends SQLContext(sc) with Logging {
         ExtractPythonUDFs ::
         ResolveHiveWindowFunction ::
         sources.PreInsertCastAndRename ::
+        ConvertAggregateFunction(self) ::
         Nil
 
       override val extendedCheckRules = Seq(