diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/command/SetCommand.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/command/SetCommand.scala
index dc8d97594c7a..1819d190aebd 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/command/SetCommand.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/command/SetCommand.scala
@@ -88,7 +88,7 @@ case class SetCommand(kv: Option[(String, Option[String])]) extends RunnableComm
     case Some(("-v", None)) =>
       val runFunc = (sparkSession: SparkSession) => {
         sparkSession.sessionState.conf.getAllDefinedConfs.map { case (key, defaultValue, doc) =>
-          Row(key, defaultValue, doc)
+          Row(key, if (defaultValue == null) "null" else defaultValue, doc)
         }
       }
       val schema = StructType(
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
index 8f1beaa3a168..049e6ed2b1aa 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
@@ -992,6 +992,10 @@ class SQLQuerySuite extends QueryTest with SharedSQLContext {
     spark.sessionState.conf.clear()
   }
 
+  test("`SET -v` collect") {
+    sql("SET -v").collect()
+  }
+
   test("apply schema") {
     val schema1 = StructType(
       StructField("f1", IntegerType, false) ::