diff --git a/src/nvim/plines.c b/src/nvim/plines.c
index 176f86c691..cbde0cfff9 100644
--- a/src/nvim/plines.c
+++ b/src/nvim/plines.c
@@ -288,8 +288,8 @@ unsigned int win_linetabsize(win_T *wp, linenr_T lnum, char_u *line, colnr_T len
 ///
 /// "line" is the start of the line, "ptr" is the first relevant character.
 /// When "lnum" is zero do not use text properties that insert text.
-void init_chartabsize_arg(chartabsize_T *cts, win_T *wp, linenr_T lnum, colnr_T col, char *line,
-                          char *ptr)
+void init_chartabsize_arg(chartabsize_T *cts, win_T *wp, linenr_T lnum FUNC_ATTR_UNUSED,
+                          colnr_T col, char *line, char *ptr)
 {
   cts->cts_win = wp;
   cts->cts_vcol = col;