diff --git a/mllib/src/main/scala/org/apache/spark/ml/feature/StringIndexer.scala b/mllib/src/main/scala/org/apache/spark/ml/feature/StringIndexer.scala
index 3a4ab9a857648..2b1592930e77b 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/feature/StringIndexer.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/feature/StringIndexer.scala
@@ -27,7 +27,7 @@ import org.apache.spark.ml.Transformer
 import org.apache.spark.ml.util.Identifiable
 import org.apache.spark.sql.DataFrame
 import org.apache.spark.sql.functions._
-import org.apache.spark.sql.types.{DoubleType, NumericType, StringType, StructType}
+import org.apache.spark.sql.types._
 import org.apache.spark.util.collection.OpenHashMap
 
 /**
@@ -229,8 +229,7 @@ class IndexToString private[ml] (
     val outputColName = $(outputCol)
     require(inputFields.forall(_.name != outputColName),
       s"Output column $outputColName already exists.")
-    val attr = NominalAttribute.defaultAttr.withName($(outputCol))
-    val outputFields = inputFields :+ attr.toStructField()
+    val outputFields = inputFields :+ StructField($(outputCol), StringType)
     StructType(outputFields)
   }
 
diff --git a/mllib/src/test/scala/org/apache/spark/ml/feature/StringIndexerSuite.scala b/mllib/src/test/scala/org/apache/spark/ml/feature/StringIndexerSuite.scala
index 05e05bdc64bb1..ddcdb5f4212be 100644
--- a/mllib/src/test/scala/org/apache/spark/ml/feature/StringIndexerSuite.scala
+++ b/mllib/src/test/scala/org/apache/spark/ml/feature/StringIndexerSuite.scala
@@ -17,6 +17,7 @@
 
 package org.apache.spark.ml.feature
 
+import org.apache.spark.sql.types.{StringType, StructType, StructField, DoubleType}
 import org.apache.spark.{SparkException, SparkFunSuite}
 import org.apache.spark.ml.attribute.{Attribute, NominalAttribute}
 import org.apache.spark.ml.param.ParamsSuite
@@ -165,4 +166,11 @@ class StringIndexerSuite extends SparkFunSuite with MLlibTestSparkContext {
         assert(a === b)
     }
   }
+
+  test("IndexToString.transformSchema (SPARK-10573)") {
+    val idxToStr = new IndexToString().setInputCol("input").setOutputCol("output")
+    val inSchema = StructType(Seq(StructField("input", DoubleType)))
+    val outSchema = idxToStr.transformSchema(inSchema)
+    assert(outSchema("output").dataType === StringType)
+  }
 }