diff --git a/src/obierrno.h b/src/obierrno.h
index fcc4eed..e9fb6c0 100644
--- a/src/obierrno.h
+++ b/src/obierrno.h
@@ -114,7 +114,7 @@ extern int obi_errno;
 	 	 	 	 	 	 	 	 	 	 	 */
 #define OBI_INDEXER_ERROR			(27)    /** Error handling a blob indexer
 											 */
-#define OBI_READ_ONLY_INDEXER_ERROR (28)    /** Error trying to modify a read-only a blob indexer
+#define OBI_READ_ONLY_INDEXER_ERROR (28)    /** Error trying to modify a read-only blob indexer
 											 */
 #define OBI_ALIGN_ERROR				(29)    /** Error while aligning sequences
  	 	 	 	 	 	 	 	 	 	 	 */