--- a/hotspot/src/share/vm/runtime/thread.cpp	Wed Aug 23 23:38:06 2017 +0200
+++ b/hotspot/src/share/vm/runtime/thread.cpp	Wed Aug 16 14:14:23 2017 +0200
@@ -2514,6 +2514,9 @@
   address low_addr = stack_end();
   size_t len = stack_guard_zone_size();
 
+  assert(is_aligned(low_addr, os::vm_page_size()), "Stack base should be the start of a page");
+  assert(is_aligned(len, os::vm_page_size()), "Stack size should be a multiple of page size");
+
   int must_commit = os::must_commit_stack_guard_pages();
   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);