diff --git a/include/avif/avif.h b/include/avif/avif.h
index dfb4e9de12..4b7e2b938e 100644
--- a/include/avif/avif.h
+++ b/include/avif/avif.h
@@ -555,6 +555,8 @@ typedef struct avifImage
     // Metadata - set with avifImageSetMetadata*() before write, check .size>0 for existence after read
     avifRWData exif;
     avifRWData xmp;
+
+    // Version 1.0.0 ends here. Add any new members after this line.
 } avifImage;
 
 // avifImageCreate() and avifImageCreateEmpty() return NULL if arguments are invalid or if a memory allocation failed.
@@ -1006,6 +1008,8 @@ typedef struct avifDecoder
 
     // Internals used by the decoder
     struct avifDecoderData * data;
+
+    // Version 1.0.0 ends here. Add any new members after this line.
 } avifDecoder;
 
 AVIF_API avifDecoder * avifDecoderCreate(void);
@@ -1172,6 +1176,8 @@ typedef struct avifEncoder
     // Internals used by the encoder
     struct avifEncoderData * data;
     struct avifCodecSpecificOptions * csOptions;
+
+    // Version 1.0.0 ends here. Add any new members after this line.
 } avifEncoder;
 
 // avifEncoderCreate() returns NULL if a memory allocation failed.