Index: src/wp-admin/load-scripts.php
===================================================================
--- src/wp-admin/load-scripts.php	(revision 50561)
+++ src/wp-admin/load-scripts.php	(working copy)
@@ -33,6 +33,11 @@
 	exit;
 }
 
+if ( isset( $_GET['script_debug'] ) && ! defined( 'SCRIPT_DEBUG' ) ) {
+	$script_debug = 'true' === $_GET['script_debug'];
+	define( 'SCRIPT_DEBUG', $script_debug );
+}
+
 require ABSPATH . 'wp-admin/includes/noop.php';
 require ABSPATH . WPINC . '/script-loader.php';
 require ABSPATH . WPINC . '/version.php';
Index: src/wp-admin/load-styles.php
===================================================================
--- src/wp-admin/load-styles.php	(revision 50561)
+++ src/wp-admin/load-styles.php	(working copy)
@@ -14,6 +14,11 @@
 
 define( 'WPINC', 'wp-includes' );
 
+if ( isset( $_GET['script_debug'] ) && ! defined( 'SCRIPT_DEBUG' ) ) {
+	$script_debug = 'true' === $_GET['script_debug'];
+	define( 'SCRIPT_DEBUG', $script_debug );
+}
+
 require ABSPATH . 'wp-admin/includes/noop.php';
 require ABSPATH . WPINC . '/script-loader.php';
 require ABSPATH . WPINC . '/version.php';
Index: src/wp-includes/script-loader.php
===================================================================
--- src/wp-includes/script-loader.php	(revision 50561)
+++ src/wp-includes/script-loader.php	(working copy)
@@ -1951,7 +1951,16 @@
 			$concatenated .= "&load%5Bchunk_{$key}%5D={$chunk}";
 		}
 
-		$src = $wp_scripts->base_url . "/wp-admin/load-scripts.php?c={$zip}" . $concatenated . '&ver=' . $wp_scripts->default_version;
+		// Pass the SCRIPT_DEBUG constant in the query args as it is usually defined
+		// in wp-config.php which is not used in load-scripts.php.
+		$script_debug = '';
+
+		if ( defined( 'SCRIPT_DEBUG' ) ) {
+			$debug = SCRIPT_DEBUG ? 'true' : 'false';
+			$script_debug = "&script_debug={$debug}";
+		}
+
+		$src = $wp_scripts->base_url . "/wp-admin/load-scripts.php?c={$zip}" . $script_debug . $concatenated . '&ver=' . $wp_scripts->default_version;
 		echo "<script{$type_attr} src='" . esc_attr( $src ) . "'></script>\n";
 	}
 
@@ -2128,7 +2137,16 @@
 			$concatenated .= "&load%5Bchunk_{$key}%5D={$chunk}";
 		}
 
-		$href = $wp_styles->base_url . "/wp-admin/load-styles.php?c={$zip}&dir={$dir}" . $concatenated . '&ver=' . $ver;
+		// Pass the SCRIPT_DEBUG constant in the query args as it is usually defined
+		// in wp-config.php which is not used in load-styles.php.
+		$script_debug = '';
+
+		if ( defined( 'SCRIPT_DEBUG' ) ) {
+			$debug = SCRIPT_DEBUG ? 'true' : 'false';
+			$script_debug = "&script_debug={$debug}";
+		}
+
+		$href = $wp_styles->base_url . "/wp-admin/load-styles.php?c={$zip}&dir={$dir}" . $script_debug . $concatenated . '&ver=' . $ver;
 		echo "<link rel='stylesheet' href='" . esc_attr( $href ) . "'{$type_attr} media='all' />\n";
 
 		if ( ! empty( $wp_styles->print_code ) ) {