diff --git a/src/dhcp/nm-dhcp-nettools.c b/src/dhcp/nm-dhcp-nettools.c
index c81823fa23..52f55655ed 100644
--- a/src/dhcp/nm-dhcp-nettools.c
+++ b/src/dhcp/nm-dhcp-nettools.c
@@ -1053,6 +1053,7 @@ dhcp4_event_cb (GIOChannel *source,
 	return G_SOURCE_CONTINUE;
 }
 
+G_GNUC_PRINTF (3, 4)
 static void
 nettools_log (int level, void *data, const char *fmt, ...)
 {