diff --git a/CHANGES b/CHANGES
index 4075e9b28a..27869baad0 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+4944.	[cleanup]	Silence cppcheck portability warnings in
+			lib/isc/tests/buffer_test.c. [GL #239]
+
 4943.	[bug]		Change 4687 consumed too much memory when running
 			system tests with --with-tuning=large.  Reduced the
 			hash table size to 512 entries for 'named -m record'
diff --git a/lib/isc/tests/buffer_test.c b/lib/isc/tests/buffer_test.c
index 9fead36a0e..70f49161c5 100644
--- a/lib/isc/tests/buffer_test.c
+++ b/lib/isc/tests/buffer_test.c
@@ -265,10 +265,15 @@ ATF_TC_BODY(isc_buffer_printf, tc) {
 
 	/*
 	 * Check an empty format string is properly handled.
+	 *
+	 * Note: we don't use a string literal for the format string to
+	 * avoid triggering [-Werror=format-zero-length].
+	 * Note: we have a dummy third argument as some compilers complain
+	 * without it.
 	 */
 	prev_used = used;
 	empty_fmt = "";
-	result = isc_buffer_printf(b, empty_fmt, NULL);
+	result = isc_buffer_printf(b, empty_fmt, "");
 	ATF_CHECK_EQ(result, ISC_R_SUCCESS);
 	used = isc_buffer_usedlength(b);
 	ATF_CHECK_EQ(prev_used, used);