diff --git a/test/unit/helpers.lua b/test/unit/helpers.lua
index 7ef2fa22fc..2cea88c8c0 100644
--- a/test/unit/helpers.lua
+++ b/test/unit/helpers.lua
@@ -704,7 +704,7 @@ local function gen_itp(it)
         itp_child(wr, func)
       else
         sc.close(wr)
-        saved_child_pid = child_pid
+        local saved_child_pid = child_pid
         child_pid = nil
         itp_parent(rd, saved_child_pid, allow_failure)
       end