diff --git a/sql/core/src/main/scala/org/apache/spark/sql/jdbc/JDBCRDD.scala b/sql/core/src/main/scala/org/apache/spark/sql/jdbc/JDBCRDD.scala
index 244bd3ebfe..88f1b02549 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/jdbc/JDBCRDD.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/jdbc/JDBCRDD.scala
@@ -53,7 +53,7 @@ private[sql] object JDBCRDD extends Logging {
       signed: Boolean): DataType = {
     val answer = sqlType match {
       case java.sql.Types.ARRAY         => null
-      case java.sql.Types.BIGINT        => LongType
+      case java.sql.Types.BIGINT        => if (signed) { LongType } else { DecimalType.Unlimited }
       case java.sql.Types.BINARY        => BinaryType
       case java.sql.Types.BIT           => BooleanType // @see JdbcDialect for quirks
       case java.sql.Types.BLOB          => BinaryType