diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
index 5a30bbdf846a2..6ccd5a451eafc 100755
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala
@@ -2714,7 +2714,8 @@ case class Base64(child: Expression, chunkBase64: Boolean)
     dataType,
     "encode",
     Seq(child, Literal(chunkBase64, BooleanType)),
-    Seq(BinaryType, BooleanType))
+    Seq(BinaryType, BooleanType),
+    returnNullable = false)
 
   override def toString: String = s"$prettyName($child)"
 
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/StringExpressionsSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/StringExpressionsSuite.scala
index 7210979f08462..b39820f0d317d 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/StringExpressionsSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/StringExpressionsSuite.scala
@@ -467,6 +467,13 @@ class StringExpressionsSuite extends SparkFunSuite with ExpressionEvalHelper {
     val b = $"b".binary.at(0)
     val bytes = Array[Byte](1, 2, 3, 4)
 
+    assert(!Base64(Literal(bytes)).nullable)
+    assert(Base64(Literal.create(null, BinaryType)).nullable)
+    assert(Base64(Literal(bytes).castNullable()).nullable)
+    assert(!UnBase64(Literal("AQIDBA==")).nullable)
+    assert(UnBase64(Literal.create(null, StringType)).nullable)
+    assert(UnBase64(Literal("AQIDBA==").castNullable()).nullable)
+
     checkEvaluation(Base64(Literal(bytes)), "AQIDBA==", create_row("abdef"))
     checkEvaluation(Base64(UnBase64(Literal("AQIDBA=="))), "AQIDBA==", create_row("abdef"))
     checkEvaluation(Base64(UnBase64(Literal(""))), "", create_row("abdef"))