diff --git a/ChangeLog b/ChangeLog
index 6f846c8fa559d985e80c19857ca72fb77fb28be7..2510b74f8d50c417dade00013d2031b7466d19ca 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -19,6 +19,7 @@
 	* testsuite/sexp-format-test.c (test_main): Likewise.
 	* testsuite/rsa-encrypt-test.c (test_main): Likewise.
 	* tools/nettle-lfib-stream.c (main): Likewise.
+	* tools/output.c (sexp_put_string): Likewise.
 
 	* testsuite/testutils.c (test_armor): Change ascii argument to
 	const char *.
diff --git a/tools/output.c b/tools/output.c
index eb4825d30f6db96df09a4cd0487be7ba0d9c279c..02e43d58547c56f82a2d6374206e102f7c9ee9e8 100644
--- a/tools/output.c
+++ b/tools/output.c
@@ -203,7 +203,7 @@ sexp_put_string(struct sexp_output *output, enum sexp_mode mode,
 {
   if (!string->size)
     sexp_put_data(output, 2,
-		  (mode == SEXP_ADVANCED) ? "\"\"": "0:");
+		  (const uint8_t *) ((mode == SEXP_ADVANCED) ? "\"\"": "0:"));
 
   else if (mode == SEXP_ADVANCED)
     {