diff --git a/src/MakeJsonCommand.php b/src/MakeJsonCommand.php
index b7ed612..1dd8257 100644
--- a/src/MakeJsonCommand.php
+++ b/src/MakeJsonCommand.php
@@ -242,7 +242,7 @@ protected function make_json( $source_file, $destination, $map ) {
 		$domain = $translations->getDomain();
 
 		if ( $domain && 0 !== strpos( $base_file_name, $domain ) ) {
-			$base_file_name = "$domain-$base_file_name";
+			$base_file_name = "{$domain}-{$base_file_name}";
 		}
 
 		foreach ( $translations as $translation ) {