diff --git a/include/mimalloc-types.h b/include/mimalloc-types.h
index 449e2e41..525a1a77 100644
--- a/include/mimalloc-types.h
+++ b/include/mimalloc-types.h
@@ -14,7 +14,9 @@ terms of the MIT license. A copy of the license can be found in the file
 
 // Minimal alignment necessary. On most platforms 16 bytes are needed
 // due to SSE registers for example. This must be at least `MI_INTPTR_SIZE`
+#ifndef MI_MAX_ALIGN_SIZE
 #define MI_MAX_ALIGN_SIZE  16   // sizeof(max_align_t)
+#endif
 
 // ------------------------------------------------------
 // Variants