diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 6c3f6eb1f790..05f12c527b02 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -497,6 +497,14 @@ void __init mem_init(void)
 
 	/* clear_bss() already clear the empty_zero_page */
 
+	/* temporary debugging - double check it's true: */
+	{
+		int i;
+
+		for (i = 0; i < 1024; i++)
+			WARN_ON_ONCE(empty_zero_page[i]);
+	}
+
 	reservedpages = 0;
 
 	/* this will put all low memory onto the freelists */