diff --git a/programs/pkey/pk_sign.c b/programs/pkey/pk_sign.c
index 9efa897..43e01f8 100644
--- a/programs/pkey/pk_sign.c
+++ b/programs/pkey/pk_sign.c
@@ -129,7 +129,7 @@
     }
 
     /*
-     * Write the signature into <filename>-sig.txt
+     * Write the signature into <filename>.sig
      */
     mbedtls_snprintf( filename, sizeof(filename), "%s.sig", argv[2] );