diff --git a/rtcore.h b/rtcore.h
index 607f9ef..e160e5d 100644
--- a/rtcore.h
+++ b/rtcore.h
@@ -141,6 +141,19 @@ typedef int32_t b32;
 	#define force_inline inline
 #endif
 
+#if __STDC_VERSION__ >= 201112L
+	/* C11 introduces _Alignof */
+	#define ALIGNOF(T) _Alignof(T)
+#else
+	#if defined(__GNUC__) || defined(__clang__)
+		/* Use the compiler-specific keyword/operator */
+		#define ALIGNOF(T) __alignof__(T)
+	#else
+		/* Fallback to the portable C89/C99 trick */
+		#define ALIGNOF(T) offsetof(struct { char c; T member; }, member)
+	#endif
+#endif
+
 /* Arena allocator */
 typedef struct arena
 {
@@ -195,9 +208,9 @@ enum
  */
 #define alloc(...) allocx(__VA_ARGS__, alloc4, alloc3, alloc2)(__VA_ARGS__)
 #define allocx(a, b, c, d, e, ...) e
-#define alloc2(a, t) (t *)ArenaAlloc(a, isizeof(t), _Alignof(t), 1, 0)
-#define alloc3(a, t, n) (t *)ArenaAlloc(a, isizeof(t), _Alignof(t), n, 0)
-#define alloc4(a, t, n, f) (t *)ArenaAlloc(a, isizeof(t), _Alignof(t), n, f)
+#define alloc2(a, t) (t *)ArenaAlloc(a, isizeof(t), ALIGNOF(t), 1, 0)
+#define alloc3(a, t, n) (t *)ArenaAlloc(a, isizeof(t), ALIGNOF(t), n, 0)
+#define alloc4(a, t, n, f) (t *)ArenaAlloc(a, isizeof(t), ALIGNOF(t), n, f)
 
 RTC_API void *ArenaAlloc(arena *a, isize size, isize align, isize n, int flags);