diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index 67fc7c1d7e..a8958ed57b 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -51,9 +51,10 @@
    e.g. in a structure initializer (or where-ever else comma expressions
    aren't permitted). */
 #define BUILD_BUG_ON_ZERO(cond) \
-    sizeof(struct { _Static_assert(!(cond), "!(" #cond ")"); })
+    (sizeof(struct { char c; _Static_assert(!(cond), "!(" #cond ")"); }) & 0)
 #else
-#define BUILD_BUG_ON_ZERO(cond) sizeof(struct { int:-!!(cond); })
+#define BUILD_BUG_ON_ZERO(cond) \
+    (sizeof(struct { unsigned u : !(cond); }) & 0)
 #define BUILD_BUG_ON(cond) ((void)BUILD_BUG_ON_ZERO(cond))
 #endif