diff --git a/lib/fts.c b/lib/fts.c
index 884b84a5a1..875fe05793 100644
--- a/lib/fts.c
+++ b/lib/fts.c
@@ -1736,11 +1736,11 @@ fd_ring_print (FTS const *sp, FILE *stream, char const *msg)
     {
       int fd = fd_ring->ir_data[i];
       if (fd < 0)
-        fprintf (stream, "%d: %d:\n", i, fd);
+        fprintf (stream, "%u: %d:\n", i, fd);
       else
         {
           struct devino wd = getdevino (fd);
-          fprintf (stream, "%d: %d: "PRINT_DEVINO"\n", i, fd, wd.dev, wd.ino);
+          fprintf (stream, "%u: %d: "PRINT_DEVINO"\n", i, fd, wd.dev, wd.ino);
         }
       if (i == fd_ring->ir_back)
         break;
diff --git a/lib/fts_.h b/lib/fts_.h
index fa3d4146e2..82da038a53 100644
--- a/lib/fts_.h
+++ b/lib/fts_.h
@@ -271,6 +271,10 @@ _GL_ATTRIBUTE_NODISCARD
 FTSENT  *fts_read (FTS *) __THROW;
 
 int      fts_set (FTS *, FTSENT *, int) __THROW;
+
+#if GNULIB_FTS_DEBUG
+void fts_cross_check (FTS const *sp);
+#endif
 __END_DECLS
 
 #endif /* fts.h */