diff --git a/lib/database.cc b/lib/database.cc
index b3ffd04d..6d0e5a63 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -2653,7 +2653,7 @@ notmuch_database_get_all_tags (notmuch_database_t *db)
 }
 
 const char *
-notmuch_database_status_string (notmuch_database_t *notmuch)
+notmuch_database_status_string (const notmuch_database_t *notmuch)
 {
     return notmuch->status_string;
 }
diff --git a/lib/notmuch.h b/lib/notmuch.h
index 8639b383..86b5b4de 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -313,7 +313,7 @@ notmuch_database_open_verbose (const char *path,
  *
  */
 const char *
-notmuch_database_status_string (notmuch_database_t *notmuch);
+notmuch_database_status_string (const notmuch_database_t *notmuch);
 
 /**
  * Commit changes and close the given notmuch database.