diff --git a/lib/client-assets.php b/lib/client-assets.php
index ef74ce9e025126..f5d881902b9a1f 100644
--- a/lib/client-assets.php
+++ b/lib/client-assets.php
@@ -233,6 +233,10 @@ function gutenberg_register_vendor_scripts( $scripts ) {
  * @param WP_Scripts $scripts WP_Scripts instance.
  */
 function gutenberg_register_packages_scripts( $scripts ) {
+	// When in production, use the plugin's version as the default asset version;
+	// else (for development or test) default to use the current time.
+	$default_version = defined( 'GUTENBERG_VERSION' ) && ! ( defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ) ? GUTENBERG_VERSION : time();
+
 	foreach ( glob( gutenberg_dir_path() . 'build/*/index.js' ) as $path ) {
 		// Prefix `wp-` to package directory to get script handle.
 		// For example, `…/build/a11y/index.js` becomes `wp-a11y`.
@@ -244,7 +248,7 @@ function gutenberg_register_packages_scripts( $scripts ) {
 			? require( $asset_file )
 			: null;
 		$dependencies = isset( $asset['dependencies'] ) ? $asset['dependencies'] : array();
-		$version      = isset( $asset['version'] ) ? $asset['version'] : filemtime( $path );
+		$version      = isset( $asset['version'] ) ? $asset['version'] : $default_version;
 
 		// Add dependencies that cannot be detected and generated by build tools.
 		switch ( $handle ) {
@@ -285,13 +289,17 @@ function gutenberg_register_packages_scripts( $scripts ) {
  * @param WP_Styles $styles WP_Styles instance.
  */
 function gutenberg_register_packages_styles( $styles ) {
+	// When in production, use the plugin's version as the asset version;
+	// else (for development or test) default to use the current time.
+	$version = defined( 'GUTENBERG_VERSION' ) && ! ( defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ) ? GUTENBERG_VERSION : time();
+
 	// Editor Styles.
 	gutenberg_override_style(
 		$styles,
 		'wp-block-editor',
 		gutenberg_url( 'build/block-editor/style.css' ),
 		array( 'wp-components' ),
-		filemtime( gutenberg_dir_path() . 'build/editor/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-block-editor', 'rtl', 'replace' );
 
@@ -300,7 +308,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-editor',
 		gutenberg_url( 'build/editor/style.css' ),
 		array( 'wp-components', 'wp-block-editor', 'wp-nux', 'wp-reusable-blocks' ),
-		filemtime( gutenberg_dir_path() . 'build/editor/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-editor', 'rtl', 'replace' );
 
@@ -309,7 +317,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-edit-post',
 		gutenberg_url( 'build/edit-post/style.css' ),
 		array( 'wp-components', 'wp-block-editor', 'wp-editor', 'wp-edit-blocks', 'wp-block-library', 'wp-nux' ),
-		filemtime( gutenberg_dir_path() . 'build/edit-post/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-edit-post', 'rtl', 'replace' );
 
@@ -318,7 +326,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-components',
 		gutenberg_url( 'build/components/style.css' ),
 		array( 'dashicons' ),
-		filemtime( gutenberg_dir_path() . 'build/components/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-components', 'rtl', 'replace' );
 
@@ -328,7 +336,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-block-library',
 		gutenberg_url( 'build/block-library/' . $block_library_filename . '.css' ),
 		array(),
-		filemtime( gutenberg_dir_path() . 'build/block-library/' . $block_library_filename . '.css' )
+		$version
 	);
 	$styles->add_data( 'wp-block-library', 'rtl', 'replace' );
 	$styles->add_data( 'wp-block-library', 'path', gutenberg_dir_path() . 'build/block-library/' . $block_library_filename . '.css' );
@@ -338,7 +346,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-format-library',
 		gutenberg_url( 'build/format-library/style.css' ),
 		array( 'wp-block-editor', 'wp-components' ),
-		filemtime( gutenberg_dir_path() . 'build/format-library/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-format-library', 'rtl', 'replace' );
 
@@ -360,7 +368,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-edit-blocks',
 		gutenberg_url( 'build/block-library/editor.css' ),
 		$wp_edit_blocks_dependencies,
-		filemtime( gutenberg_dir_path() . 'build/block-library/editor.css' )
+		$version
 	);
 	$styles->add_data( 'wp-edit-blocks', 'rtl', 'replace' );
 
@@ -369,7 +377,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-nux',
 		gutenberg_url( 'build/nux/style.css' ),
 		array( 'wp-components' ),
-		filemtime( gutenberg_dir_path() . 'build/nux/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-nux', 'rtl', 'replace' );
 
@@ -378,7 +386,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-block-library-theme',
 		gutenberg_url( 'build/block-library/theme.css' ),
 		array(),
-		filemtime( gutenberg_dir_path() . 'build/block-library/theme.css' )
+		$version
 	);
 	$styles->add_data( 'wp-block-library-theme', 'rtl', 'replace' );
 
@@ -387,7 +395,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-list-reusable-blocks',
 		gutenberg_url( 'build/list-reusable-blocks/style.css' ),
 		array( 'wp-components' ),
-		filemtime( gutenberg_dir_path() . 'build/list-reusable-blocks/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-list-reusable-block', 'rtl', 'replace' );
 
@@ -396,7 +404,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-edit-navigation',
 		gutenberg_url( 'build/edit-navigation/style.css' ),
 		array( 'wp-components', 'wp-block-editor', 'wp-edit-blocks' ),
-		filemtime( gutenberg_dir_path() . 'build/edit-navigation/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-edit-navigation', 'rtl', 'replace' );
 
@@ -405,7 +413,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-edit-site',
 		gutenberg_url( 'build/edit-site/style.css' ),
 		array( 'wp-components', 'wp-block-editor', 'wp-edit-blocks' ),
-		filemtime( gutenberg_dir_path() . 'build/edit-site/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-edit-site', 'rtl', 'replace' );
 
@@ -414,7 +422,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-edit-widgets',
 		gutenberg_url( 'build/edit-widgets/style.css' ),
 		array( 'wp-components', 'wp-block-editor', 'wp-edit-blocks', 'wp-reusable-blocks' ),
-		filemtime( gutenberg_dir_path() . 'build/edit-widgets/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-edit-widgets', 'rtl', 'replace' );
 
@@ -423,7 +431,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-block-directory',
 		gutenberg_url( 'build/block-directory/style.css' ),
 		array( 'wp-block-editor', 'wp-components' ),
-		filemtime( gutenberg_dir_path() . 'build/block-directory/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-block-directory', 'rtl', 'replace' );
 
@@ -432,7 +440,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-customize-widgets',
 		gutenberg_url( 'build/customize-widgets/style.css' ),
 		array( 'wp-components', 'wp-block-editor', 'wp-edit-blocks' ),
-		filemtime( gutenberg_dir_path() . 'build/customize-widgets/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-customize-widgets', 'rtl', 'replace' );
 
@@ -441,7 +449,7 @@ function gutenberg_register_packages_styles( $styles ) {
 		'wp-reusable-blocks',
 		gutenberg_url( 'build/reusable-blocks/style.css' ),
 		array( 'wp-components' ),
-		filemtime( gutenberg_dir_path() . 'build/reusable-blocks/style.css' )
+		$version
 	);
 	$styles->add_data( 'wp-reusable-block', 'rtl', 'replace' );
 }