diff --git a/lib/class-wp-theme-json-gutenberg.php b/lib/class-wp-theme-json-gutenberg.php
index 364d87d50d38f..d76fcec88cc02 100644
--- a/lib/class-wp-theme-json-gutenberg.php
+++ b/lib/class-wp-theme-json-gutenberg.php
@@ -586,7 +586,7 @@ private static function compute_style_properties( $styles, $settings = array(),
 			if ( is_array( $value_path ) ) {
 				$path_string = implode( '.', $value_path );
 				if (
-					isset( self::PROTECTED_PROPERTIES[ $path_string ] ) &&
+					array_key_exists( $path_string, self::PROTECTED_PROPERTIES ) &&
 					_wp_array_get( $settings, self::PROTECTED_PROPERTIES[ $path_string ], null ) === null
 				) {
 					continue;