diff --git a/src/include/c.h b/src/include/c.h
index bd122f6a56b7bd5061d44c7a048545f9678cb1ba..492648cd8a57220008adc9e6ed972ecf9644e614 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -446,7 +446,7 @@ struct varlena
 /*
  * These widely-used datatypes are just a varlena header and the data bytes.
  * There is no terminating null or anything like that --- the data length is
- * always VARSIZE(ptr) - VARHDRSZ.
+ * always VARSIZE_ANY_EXHDR(ptr).
  */
 typedef struct varlena bytea;
 typedef struct varlena text;