diff --git a/src/nvim/mouse.c b/src/nvim/mouse.c
index 9c6acf9f80..aca15eb0e2 100644
--- a/src/nvim/mouse.c
+++ b/src/nvim/mouse.c
@@ -1692,7 +1692,8 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
   // highlighting the second byte, not the ninth.
 
   linenr_T lnum = wp->w_cursor.lnum;
-  char *line = ml_get(lnum);
+  // Make a copy of the line, because syntax matching may free it.
+  char *line = xstrdup(ml_get(lnum));
   char *ptr = line;
   char *ptr_end;
   char *ptr_row_offset = line;  // Where we begin adjusting `ptr_end`
@@ -1733,8 +1734,8 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
 
   vcol = offset;
 
-#define INCR() nudge++; ptr_end += utfc_ptr2len((char *)ptr_end)
-#define DECR() nudge--; ptr_end -= utfc_ptr2len((char *)ptr_end)
+#define INCR() nudge++; ptr_end += utfc_ptr2len(ptr_end)
+#define DECR() nudge--; ptr_end -= utfc_ptr2len(ptr_end)
 
   while (ptr < ptr_end && *ptr != NUL) {
     int cwidth = win_chartabsize(curwin, ptr, vcol);
@@ -1776,6 +1777,7 @@ static int mouse_adjust_click(win_T *wp, int row, int col)
     ptr += utfc_ptr2len(ptr);
   }
 
+  xfree(line);
   return col + nudge;
 }
 
diff --git a/test/functional/ui/mouse_spec.lua b/test/functional/ui/mouse_spec.lua
index d8739e1c31..621855f051 100644
--- a/test/functional/ui/mouse_spec.lua
+++ b/test/functional/ui/mouse_spec.lua
@@ -1024,13 +1024,15 @@ describe('ui/mouse/input', function()
       })
       feed('ggdG')
 
-      feed_command('set concealcursor=ni')
-      feed_command('set nowrap')
-      feed_command('set shiftwidth=2 tabstop=4 list')
-      feed_command('setl listchars=tab:>-')
-      feed_command('syntax match NonText "\\*" conceal')
-      feed_command('syntax match NonText "cats" conceal cchar=X')
-      feed_command('syntax match NonText "x" conceal cchar=>')
+      command([[setlocal concealcursor=ni nowrap shiftwidth=2 tabstop=4 list listchars=tab:>-]])
+      command([[syntax region X0 matchgroup=X1 start=/\*/ end=/\*/ concealends contains=X2]])
+      command([[syntax match X2 /cats/ conceal cchar=X contained]])
+      -- No heap-use-after-free with multi-line syntax pattern #24317
+      command([[syntax match X3 /\n\@<=x/ conceal cchar=>]])
+      command([[highlight link X0 Normal]])
+      command([[highlight link X1 NonText]])
+      command([[highlight link X2 NonText]])
+      command([[highlight link X3 NonText]])
 
       -- First column is there to retain the tabs.
       insert([[