diff --git a/src/ivfflat.h b/src/ivfflat.h
index 5620ef9..9d58b39 100644
--- a/src/ivfflat.h
+++ b/src/ivfflat.h
@@ -315,7 +315,7 @@ typedef struct IvfflatScanOpaqueData
 
 typedef IvfflatScanOpaqueData * IvfflatScanOpaque;
 
-#define VECTOR_ARRAY_SIZE(_length, _size) (sizeof(VectorArrayData) + (_length) * MAXALIGN(_size))
+#define VECTOR_ARRAY_SIZE(_length, _size) add_size(sizeof(VectorArrayData), mul_size(_length, MAXALIGN(_size)))
 
 /* Use functions instead of macros to avoid double evaluation */