diff --git a/src/calibre/utils/fonts/sfnt/cff/writer.py b/src/calibre/utils/fonts/sfnt/cff/writer.py
index 6f77dc4b98..0e229c8938 100644
--- a/src/calibre/utils/fonts/sfnt/cff/writer.py
+++ b/src/calibre/utils/fonts/sfnt/cff/writer.py
@@ -124,10 +124,11 @@ class Subset(object):
         charsets = Charsets(strings)
         charsets.extend(cff.charset[1:]) # .notdef is not included
 
+        endchar_operator = bytes(bytearray([14]))
         for i in xrange(self.cff.num_glyphs):
             cname = self.cff.charset.safe_lookup(i)
             ok = cname in keep_charnames
-            cs = self.cff.char_strings[i] if ok else b''
+            cs = self.cff.char_strings[i] if ok else endchar_operator
             char_strings.append(cs)
             if ok:
                 self.charname_map[cname] = i
diff --git a/src/calibre/utils/fonts/sfnt/subset.py b/src/calibre/utils/fonts/sfnt/subset.py
index c0dac76e30..1f675a73ba 100644
--- a/src/calibre/utils/fonts/sfnt/subset.py
+++ b/src/calibre/utils/fonts/sfnt/subset.py
@@ -96,12 +96,7 @@ def subset(raw, individual_chars, ranges=()):
         subset_truetype(sfnt, character_map)
     elif b'CFF ' in sfnt:
         # PostScript Outlines
-        from calibre.utils.config_base import tweaks
-        if tweaks['subset_cff_table']:
-            subset_postscript(sfnt, character_map)
-        else:
-            raise UnsupportedFont('This font contains PostScript outlines, '
-                'subsetting not supported')
+        subset_postscript(sfnt, character_map)
     else:
         raise UnsupportedFont('This font does not contain TrueType '
                 'or PostScript outlines')