diff --git a/src/wp-includes/class.wp-scripts.php b/src/wp-includes/class.wp-scripts.php
index 649f086d60..f20964ead4 100644
--- a/src/wp-includes/class.wp-scripts.php
+++ b/src/wp-includes/class.wp-scripts.php
@@ -501,12 +501,17 @@ class WP_Scripts extends WP_Dependencies {
 				),
 				'5.7.0'
 			);
+
+			if ( false === $l10n ) {
+				// This should really not be needed, but is necessary for backward compatibility.
+				$l10n = array( $l10n );
+			}
 		}
 
 		if ( is_string( $l10n ) ) {
 			$l10n = html_entity_decode( $l10n, ENT_QUOTES, 'UTF-8' );
-		} else {
-			foreach ( (array) $l10n as $key => $value ) {
+		} elseif ( is_array( $l10n ) ) {
+			foreach ( $l10n as $key => $value ) {
 				if ( ! is_scalar( $value ) ) {
 					continue;
 				}
diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index e799247352..9a85ee34f0 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -1428,17 +1428,8 @@ JS;
 	 *
 	 * @param mixed  $l10n_data Localization data passed to wp_localize_script().
 	 * @param string $expected  Expected transformation of localization data.
-	 * @param string $warning   Optional. Whether a PHP native warning/error is expected. Default false.
 	 */
-	public function test_wp_localize_script_data_formats( $l10n_data, $expected, $warning = false ) {
-		if ( $warning ) {
-			if ( PHP_VERSION_ID < 80000 ) {
-				$this->expectWarning();
-			} else {
-				$this->expectError();
-			}
-		}
-
+	public function test_wp_localize_script_data_formats( $l10n_data, $expected ) {
 		if ( ! is_array( $l10n_data ) ) {
 			$this->setExpectedIncorrectUsage( 'WP_Scripts::localize' );
 		}
@@ -1460,7 +1451,6 @@ JS;
 	 *
 	 *     @type mixed  $l10n_data Localization data passed to wp_localize_script().
 	 *     @type string $expected  Expected transformation of localization data.
-	 *     @type string $warning   Optional. Whether a PHP native warning/error is expected.
 	 * }
 	 */
 	public function data_wp_localize_script_data_formats() {
@@ -1471,14 +1461,16 @@ JS;
 			array( array( 'foo' => array( 'bar' => 'foobar' ) ), '{"foo":{"bar":"foobar"}}' ),
 			array( array( 'foo' => 6.6 ), '{"foo":"6.6"}' ),
 			array( array( 'foo' => 6 ), '{"foo":"6"}' ),
+			array( array(), '[]' ),
 
 			// Unofficially supported format.
 			array( 'string', '"string"' ),
 
 			// Unsupported formats.
-			array( 1.5, '1.5', true ),
-			array( 1, '1', true ),
+			array( 1.5, '1.5' ),
+			array( 1, '1' ),
 			array( false, '[""]' ),
+			array( null, 'null' ),
 		);
 	}