diff --git a/src/document.rs b/src/document.rs
index e9eedd5d9c..5cfbf71959 100644
--- a/src/document.rs
+++ b/src/document.rs
@@ -16,7 +16,7 @@ fn print_directives(directives: &[Positioned<ConstDirective>]) -> String {
         .join(" ");
 
     if !directives.is_empty() {
-        directives += " "
+        directives.push(' ')
     }
 
     directives