diff --git a/libnfc/mirror-subr.c b/libnfc/mirror-subr.c
index c457af5..f1da337 100644
--- a/libnfc/mirror-subr.c
+++ b/libnfc/mirror-subr.c
@@ -59,7 +59,7 @@ mirror (uint8_t bt)
   return ByteMirror[bt];
 }
 
-void
+static void
 mirror_bytes (uint8_t *pbts, size_t szLen)
 {
   size_t  szByteNr;