diff --git a/src/syntax.c b/src/syntax.c
index ea8d541..468dee0 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -1542,10 +1542,12 @@
  * lnum ->  line below window
  */
     void
-syntax_end_parsing(linenr_T lnum)
+syntax_end_parsing(win_T *wp, linenr_T lnum)
 {
     synstate_T	*sp;
 
+    if (syn_block != wp->w_s)
+	return;  // not the right window
     sp = syn_stack_find_entry(lnum);
     if (sp != NULL && sp->sst_lnum < lnum)
 	sp = sp->sst_next;