diff --git a/tests/lua53/strings.lua b/tests/lua53/strings.lua
index ca90051..6a05cf6 100644
--- a/tests/lua53/strings.lua
+++ b/tests/lua53/strings.lua
@@ -437,7 +437,7 @@ else
 
   -- formats %U, %f, %I already tested elsewhere
 
-  local blen = 400    -- internal buffer length in 'luaO_pushfstring'
+  local blen = 200    -- internal buffer length in 'luaO_pushfstring'
 
   local function callpfs (op, fmt, n)
     local x = {T.testC("pushfstring" .. op .. "; return *", fmt, n)}