diff --git a/src/wp-includes/blocks.php b/src/wp-includes/blocks.php
index 9a8c3b06f4..787ba44d2c 100644
--- a/src/wp-includes/blocks.php
+++ b/src/wp-includes/blocks.php
@@ -260,7 +260,11 @@ function register_block_style_handle( $metadata, $field_name, $index = 0 ) {
 	if ( $has_style_file ) {
 		wp_style_add_data( $style_handle, 'path', $style_path_norm );
 
-		$rtl_file = str_replace( "{$suffix}.css", "-rtl{$suffix}.css", $style_path_norm );
+		if ( $is_core_block ) {
+			$rtl_file = str_replace( "{$suffix}.css", "-rtl{$suffix}.css", $style_path_norm );
+		} else {
+			$rtl_file = str_replace( ".css", "-rtl.css", $style_path_norm );
+		}
 
 		if ( is_rtl() && file_exists( $rtl_file ) ) {
 			wp_style_add_data( $style_handle, 'rtl', 'replace' );