diff --git a/includes/classes/Feature/Documents/Documents.php b/includes/classes/Feature/Documents/Documents.php
index 29ee7352e..f7e0d552b 100644
--- a/includes/classes/Feature/Documents/Documents.php
+++ b/includes/classes/Feature/Documents/Documents.php
@@ -128,8 +128,14 @@ public function setup_document_search( $query ) {
 			return;
 		}
 
+		// Return if attachments are not involved in the query.
+		// If post_type is empty, attachments will be included automatically.
+		$post_type = (array) $query->get( 'post_type', [] );
+		if ( ! empty( $post_type ) && ! in_array( 'attachment', $post_type, true ) ) {
+			return;
+		}
+
 		$this->maybe_set_post_status( $query );
-		$this->maybe_set_post_type( $query );
 		$this->maybe_set_mime_type( $query );
 	}
 
@@ -523,24 +529,6 @@ protected function maybe_set_post_status( $query ) {
 		$query->set( 'post_status', array_unique( $post_status ) );
 	}
 
-	/**
-	 * Add the attachment post type to post_type.
-	 *
-	 * @param WP_Query $query WP_Query to modify to search.
-	 * @return void
-	 */
-	protected function maybe_set_post_type( $query ) {
-		$post_type = $query->get( 'post_type', [] );
-		if ( empty( $post_type ) || ! is_string( $post_type ) || 'any' === $post_type ) {
-			return;
-		}
-
-		$post_type   = explode( ' ', $post_type );
-		$post_type[] = 'attachment';
-
-		$query->set( 'post_type', array_unique( $post_type ) );
-	}
-
 	/**
 	 * Add allowed mime types. If mime types are already set, append.
 	 *
diff --git a/tests/php/features/TestDocuments.php b/tests/php/features/TestDocuments.php
index ee9b85036..eb3525a5d 100644
--- a/tests/php/features/TestDocuments.php
+++ b/tests/php/features/TestDocuments.php
@@ -300,4 +300,57 @@ public function test_ep_allowed_documents_ingest_mime_types_filter() {
 
 		$this->assertSame( 'text/test', $feature->get_allowed_ingest_mime_types()['test'] );
 	}
+
+	/**
+	 * Depending on the WP_Query post_type parameter, attachments should be added by default.
+	 *
+	 * @since 5.1.0
+	 * @group documents
+	 */
+	public function test_empty_post_type() {
+		ElasticPress\Features::factory()->activate_feature( 'search' );
+		ElasticPress\Features::factory()->activate_feature( 'documents' );
+		ElasticPress\Features::factory()->setup_features();
+
+		$this->ep_factory->post->create(
+			array(
+				'post_title' => 'findme',
+				'post_type'  => 'post',
+			)
+		);
+		$this->ep_factory->post->create(
+			array(
+				'post_title'     => 'findme',
+				'post_type'      => 'attachment',
+				'post_mime_type' => 'application/msword',
+			)
+		);
+
+		ElasticPress\Elasticsearch::factory()->refresh_indices();
+
+		// No post type, attachment added by default
+		$query = new \WP_Query( [ 's' => 'findme' ] );
+		$this->assertTrue( $query->elasticsearch_success );
+		$this->assertEquals( 2, $query->post_count );
+
+		// Post type as string, attachment not added by default
+		$query = new \WP_Query(
+			[
+				'post_type' => 'post',
+				's'         => 'findme',
+			]
+		);
+		$this->assertTrue( $query->elasticsearch_success );
+		$this->assertEquals( 1, $query->post_count );
+
+		// Post type as array, attachment not added by default
+		$query = new \WP_Query(
+			[
+				'post_type' => [ 'post' ],
+				's'         => 'findme',
+			]
+		);
+		$this->assertTrue( $query->elasticsearch_success );
+		$this->assertEquals( 1, $query->post_count );
+	}
 }
diff --git a/tests/php/features/TestFacetTypeDate.php b/tests/php/features/TestFacetTypeDate.php
index f3a3df3f8..65d5379aa 100644
--- a/tests/php/features/TestFacetTypeDate.php
+++ b/tests/php/features/TestFacetTypeDate.php
@@ -26,6 +26,10 @@ class TestFacetTypeDate extends BaseTestCase {
 	 * Setup each test.
 	 */
 	public function set_up() {
+		ElasticPress\Elasticsearch::factory()->delete_all_indices();
+		ElasticPress\Indexables::factory()->get( 'post' )->put_mapping();
+		ElasticPress\Indexables::factory()->get( 'post' )->sync_manager->reset_sync_queue();
+
 		$facet_feature    = Features::factory()->get_registered_feature( 'facets' );
 		$this->facet_type = $facet_feature->types['date'];
 
@@ -332,6 +336,7 @@ public function testQueryPost() {
 				'ep_integrate' => true,
 			]
 		);
+		$this->assertTrue( $query->elasticsearch_success );
 		$this->assertEquals( 2, $query->found_posts );
 
 		// get all posts published on or after 2022-01-01.
@@ -341,6 +346,7 @@ public function testQueryPost() {
 				'ep_integrate' => true,
 			]
 		);
+		$this->assertTrue( $query->elasticsearch_success );
 		$this->assertEquals( 4, $query->found_posts );
 
 		// get all posts published on or before 2022-01-01.
@@ -350,6 +356,7 @@ public function testQueryPost() {
 				'ep_integrate' => true,
 			]
 		);
+		$this->assertTrue( $query->elasticsearch_success );
 		$this->assertEquals( 2, $query->found_posts );
 
 		// passing invalid date shouldn't apply any filter.
@@ -359,6 +366,7 @@ public function testQueryPost() {
 				'ep_integrate' => true,
 			]
 		);
+		$this->assertTrue( $query->elasticsearch_success );
 		$this->assertEquals( 5, $query->found_posts );
 	}
 }