diff --git a/src/core/execute.c b/src/core/execute.c
index 492df2fedb..be03695776 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -2040,7 +2040,7 @@ static int apply_working_directory(
 
                 d = wd;
         } else
-                d = strjoina(strempty(context->root_directory), "/", strempty(wd));
+                d = prefix_roota(context->root_directory, wd);
 
         if (chdir(d) < 0 && !context->working_directory_missing_ok)
                 return -errno;