diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index fad0bda..d8a7243 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -2842,8 +2842,14 @@
 		if (eap->nextcmd != NULL)
 		    ++eap->nextcmd;
 	    }
-	    if (vim9script && has_cmdmod(cmod, FALSE))
-		*errormsg = _(e_command_modifier_without_command);
+	    if (vim9script)
+	    {
+		if (has_cmdmod(cmod, FALSE))
+		    *errormsg = _(e_command_modifier_without_command);
+		if (eap->cmd[0] == '#' && eap->cmd[1] == '{'
+							 && eap->cmd[2] != '{')
+		    *errormsg = _(e_cannot_use_hash_curly_to_start_comment);
+	    }
 	    return FAIL;
 	}
 	if (*eap->cmd == NUL)