diff --git a/src/thread/ntapi_tt_create_thread.c b/src/thread/ntapi_tt_create_thread.c
index 9105ec0..a76fec9 100644
--- a/src/thread/ntapi_tt_create_thread.c
+++ b/src/thread/ntapi_tt_create_thread.c
@@ -52,6 +52,8 @@ int32_t __stdcall __ntapi_tt_create_thread(
 	nt_user_stack		stack   __attr_aligned__(0x10);
 	uintptr_t		fsuspended;
 	uintptr_t *		parg;
+	size_t			size;
+	size_t			commit;
 
 	if (!(params->stack_size_commit))
 		return NT_STATUS_INVALID_PARAMETER;
@@ -119,17 +121,17 @@ int32_t __stdcall __ntapi_tt_create_thread(
 			- params->stack_size_commit);
 
 	/* guard page */
-	params->stack_size_commit += __PAGE_SIZE;
+	commit = params->stack_size_commit + __PAGE_SIZE;
 	stack_system_limit =
 		(void *)((intptr_t)stack.expandable_stack_base
-			- params->stack_size_commit);
+			- commit);
 
 	/* then we commit */
 	status = __ntapi->zw_allocate_virtual_memory(
 		params->hprocess,
 		&stack_system_limit,
 		0,
-		&params->stack_size_commit,
+		&commit,
 		NT_MEM_COMMIT,
 		NT_PAGE_READWRITE);
 
@@ -140,11 +142,11 @@ int32_t __stdcall __ntapi_tt_create_thread(
 		status);
 
 	/* finally we protect the guard page */
-	params->stack_size_commit = __PAGE_SIZE;
+	size = __PAGE_SIZE;
 	status = __ntapi->zw_protect_virtual_memory(
 		params->hprocess,
 		&stack_system_limit,
-		&params->stack_size_commit,
+		&size,
 		NT_PAGE_READWRITE | NT_MEM_PAGE_GUARD,
 		&protect_type_old);