diff --git a/velox/functions/prestosql/MapTopN.h b/velox/functions/prestosql/MapTopN.h
index 1407dc0680f71..a2b9ba4229339 100644
--- a/velox/functions/prestosql/MapTopN.h
+++ b/velox/functions/prestosql/MapTopN.h
@@ -60,11 +60,6 @@ struct MapTopNFunction {
       return;
     }
 
-    if (n >= inputMap.size()) {
-      out.copy_from(inputMap);
-      return;
-    }
-
     using It = typename arg_type<Map<Orderable<T1>, Orderable<T2>>>::Iterator;
 
     Compare<It> comparator;
diff --git a/velox/functions/prestosql/tests/MapTopNTest.cpp b/velox/functions/prestosql/tests/MapTopNTest.cpp
index ca3e758e7884c..75e4f3984cc8f 100644
--- a/velox/functions/prestosql/tests/MapTopNTest.cpp
+++ b/velox/functions/prestosql/tests/MapTopNTest.cpp
@@ -66,6 +66,22 @@ TEST_F(MapTopNTest, basic) {
       "n must be greater than or equal to 0");
 }
 
+TEST_F(MapTopNTest, nestedNullFailure) {
+  auto data = makeMapVector(
+      /*offsets=*/{0},
+      /*keyVector=*/makeFlatVector<int32_t>({1, 2, 3}),
+      /*valueVector=*/
+      makeNullableArrayVector<int32_t>({{std::nullopt}, {2}, {5}}));
+
+  // Nested nulls present inhibit the orderbility of values. Expect an error.
+  VELOX_ASSERT_THROW(
+      evaluate("map_top_n(c0, 1)", makeRowVector({data})),
+      "Ordering nulls is not supported");
+  VELOX_ASSERT_THROW(
+      evaluate("map_top_n(c0, 10)", makeRowVector({data})),
+      "Ordering nulls is not supported");
+}
+
 // Test to ensure we use keys to break ties if values are
 // equal.
 TEST_F(MapTopNTest, equalValues) {