diff --git a/src/highlight.c b/src/highlight.c
index 79501d2..6716da0 100644
--- a/src/highlight.c
+++ b/src/highlight.c
@@ -469,7 +469,7 @@
  * the user to override the color values. Only loaded once.
  */
     static void
-load_default_colors_lists()
+load_default_colors_lists(void)
 {
     // Lacking a default color list isn't the end of the world but it is likely
     // an inconvenience so users should know when it is missing.