diff --git a/win32/win32.c b/win32/win32.c
index c4678b1593..a02ac5d9fb 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -482,8 +482,8 @@ init_env(void)
     BOOL f;
 #define env wk.val
 #define set_env_val(vname) do { \
-	typedef char namesizecheck[numberof(wk.name) < numberof(vname) - 1 ? -1 : 1]; \
-	WCHAR *const buf = wk.name + numberof(wk.name) - numberof(vname) + 1; \
+	typedef char wk_name_offset[(numberof(wk.name) - numberof(vname) + 1) * 2 + 1]; \
+	WCHAR *const buf = wk.name + sizeof(wk_name_offset) / 2; \
 	MEMCPY(buf, vname, WCHAR, numberof(vname) - 1); \
 	_wputenv(buf); \
     } while (0)