diff --git a/lisp/international/fontset.el b/lisp/international/fontset.el
index 84790adf7c1..b72c68d9d59 100644
--- a/lisp/international/fontset.el
+++ b/lisp/international/fontset.el
@@ -649,7 +649,7 @@
 	     (nil . "MuleArabic-2")
 	     (nil . "ISO8859-6"))
      (mongolian ,(font-spec :registry "iso10646-1"
-			    :otf '(mong nil (init medi fina))))
+			    :otf '(mong nil (init medi fina isol))))
 
      (hebrew ,(font-spec :registry "iso10646-1" :script 'hebrew)
 	     (nil . "ISO8859-8"))