diff --git a/tests/func/010.phpt b/tests/func/010.phpt
index f970283dc47..6d5c30c9eee 100644
--- a/tests/func/010.phpt
+++ b/tests/func/010.phpt
@@ -8,7 +8,7 @@ if (getenv("SKIP_SLOW_TESTS")) die("skip slow test");
 <?php
 
 // the stack size + some random constant
-$boundary = 64*1024;
+$boundary = 16*1024-16;
 $limit    = $boundary+42;