diff -up Python-3.7.0b3/Programs/_testembed.c.omv~ Python-3.7.0b3/Programs/_testembed.c
--- Python-3.7.0b3/Programs/_testembed.c.omv~	2018-03-29 20:36:39.714454073 +0200
+++ Python-3.7.0b3/Programs/_testembed.c	2018-03-29 20:36:51.577482603 +0200
@@ -174,8 +174,8 @@ static int test_pre_initialization_sys_o
     wchar_t *static_xoption = L"also_not_an_option=2";
     size_t warnoption_len = wcslen(static_warnoption);
     size_t xoption_len = wcslen(static_xoption);
-    wchar_t *dynamic_once_warnoption = calloc(warnoption_len+1, sizeof(wchar_t));
-    wchar_t *dynamic_xoption = calloc(xoption_len+1, sizeof(wchar_t));
+    wchar_t *dynamic_once_warnoption = (wchar_t*)calloc(warnoption_len+1, sizeof(wchar_t));
+    wchar_t *dynamic_xoption = (wchar_t*)calloc(xoption_len+1, sizeof(wchar_t));
     wcsncpy(dynamic_once_warnoption, static_warnoption, warnoption_len+1);
     wcsncpy(dynamic_xoption, static_xoption, xoption_len+1);