diff --git a/faiss/IndexFlatCodes.h b/faiss/IndexFlatCodes.h
index 6e23f88d30..a8d51b1a1a 100644
--- a/faiss/IndexFlatCodes.h
+++ b/faiss/IndexFlatCodes.h
@@ -24,9 +24,9 @@ struct IndexFlatCodes : Index {
 
     /// encoded dataset, size ntotal * code_size
     std::vector<uint8_t> codes;
-    uint8_t* codes_ptr;
     bool mmaped; // true if codes_ptr is pointing to a mmaped region
     size_t mmaped_size;
+    uint8_t* codes_ptr;
 
     IndexFlatCodes();