diff --git a/fontland/fontland/subset.rkt b/fontland/fontland/subset.rkt
index 10ad1500..5abb3332 100644
--- a/fontland/fontland/subset.rkt
+++ b/fontland/fontland/subset.rkt
@@ -284,15 +284,23 @@ https://github.com/mbutterick/fontkit/blob/master/src/subset/TTFSubset.js
 
   (define new-tables
     (let ()
+      ;; unhinted ttfs don't have `cvt_` `prep` or `fpgm`;
+      ;; so fill in dummy data
       (define kvs (dictify 'head new-head-table
                            'hhea new-hhea-table
                            'loca (ttf-subset-loca ss)
                            'maxp new-maxp-table
-                           'cvt_ (get-cvt_-table (subset-font ss))
-                           'prep (get-prep-table (subset-font ss))
+                           'cvt_ (if (has-table? (subset-font ss) 'cvt_)
+                                     (get-cvt_-table (subset-font ss))
+                                     (hash 'controlValues (list 0)))
+                           'prep (if (has-table? (subset-font ss) 'prep)
+                                     (get-prep-table (subset-font ss))
+                                     (hash 'controlValueProgram (list 0)))
                            'glyf (ttf-subset-glyf ss)
                            'hmtx (ttf-subset-hmtx ss)
-                           'fpgm (get-fpgm-table (subset-font ss))))
+                           'fpgm (if (has-table? (subset-font ss) 'fpgm)
+                                     (get-fpgm-table (subset-font ss))
+                                     (hash 'instructions (list 0)))))
       (for ([(k v) (in-dict kvs)]
             #:unless v)
         (error 'encode (format "missing value for ~a" k)))