diff --git a/packages/block-library/src/gallery/index.php b/packages/block-library/src/gallery/index.php
index dd7c37239f3127..1e5b21e067c66d 100644
--- a/packages/block-library/src/gallery/index.php
+++ b/packages/block-library/src/gallery/index.php
@@ -32,3 +32,21 @@ function render_block_core_gallery_data( $parsed_block ) {
 }
 
 add_filter( 'render_block_data', 'render_block_core_gallery_data' );
+
+/**
+ * Registers the `core/gallery` block on server.
+ * This render callback needs to be here
+ * so that the gallery styles are loaded in block-based themes.
+ */
+function gutenberg_register_block_core_gallery() {
+	register_block_type_from_metadata(
+		__DIR__ . '/gallery',
+		array(
+			'render_callback' => function ( $attributes, $content ) {
+				return $content;
+			},
+		)
+	);
+}
+
+add_action( 'init', 'gutenberg_register_block_core_gallery', 20 );
diff --git a/packages/block-library/src/image/index.php b/packages/block-library/src/image/index.php
index fc442659d5509d..4e149a9c13fcea 100644
--- a/packages/block-library/src/image/index.php
+++ b/packages/block-library/src/image/index.php
@@ -29,7 +29,7 @@ function render_block_core_image( $attributes, $content ) {
 
 
 /**
- * Register image block.
+ * Registers the `core/image` block on server.
  */
 function register_block_core_image() {
 	register_block_type_from_metadata(