diff --git a/src/option.c b/src/option.c
index dd44fe4..535213c 100644
--- a/src/option.c
+++ b/src/option.c
@@ -1306,9 +1306,10 @@
 	    // remember character after option name
 	    afterchar = arg[len];
 
-	    // skip white space, allow ":set ai  ?"
-	    while (VIM_ISWHITE(arg[len]))
-		++len;
+	    if (!in_vim9script())
+		// skip white space, allow ":set ai  ?", ":set hlsearch  !"
+		while (VIM_ISWHITE(arg[len]))
+		    ++len;
 
 	    adding = FALSE;
 	    prepending = FALSE;