diff --git a/search.c b/search.c
index 9e59c618..2e31d6d4 100644
--- a/search.c
+++ b/search.c
@@ -609,6 +609,8 @@ search_match_to_end_of_word(struct terminal *term, bool spaces_only)
     struct coord new_end = old_end;
     struct row *row = NULL;
 
+    /* Advances a coordinate by one column, to the right. Returns
+     * false if we’ve reached the scrollback wrap-around */
 #define advance_pos(coord) __extension__                                \
         ({                                                              \
             bool wrapped_around = false;                                \