diff --git a/src/calibre/utils/fonts/sfntly.cpp b/src/calibre/utils/fonts/sfntly.cpp
index adbdbd779a..d8a3b37a60 100644
--- a/src/calibre/utils/fonts/sfntly.cpp
+++ b/src/calibre/utils/fonts/sfntly.cpp
@@ -114,7 +114,7 @@ FontSourcedInfoBuilder::~FontSourcedInfoBuilder() { }
 
 CALLER_ATTACH FontInfo* FontSourcedInfoBuilder::GetFontInfo() {
     if (!cmap_) {
-        PyErr_SetString(Error, "This font has no cmap table!");
+        PyErr_SetString(UnsupportedFont, "This font has no format 4 cmap table (usually symbol or asian fonts), subsetting is not supported");
         return NULL;
     }
     CharacterMap* chars_to_glyph_ids = new CharacterMap;
@@ -515,6 +515,11 @@ do_subset(const char *data, Py_ssize_t sz, Ptr<CharacterPredicate> &predicate) {
         PyErr_SetString(Error, "Loaded font has 0 tables.");
         return NULL;
     }
+    Ptr<CMapTable> cmap_table = down_cast<CMapTable*>(font->GetTable(Tag::cmap));
+    if (!cmap_table) {
+        PyErr_SetString(Error, "Loaded font has no cmap table.");
+        return NULL;
+    }
     Ptr<PredicateSubsetter> subsetter = new PredicateSubsetter(font, predicate);
     Ptr<Font> new_font;
     new_font.Attach(subsetter->Subset());
diff --git a/src/calibre/utils/fonts/subset.py b/src/calibre/utils/fonts/subset.py
index 4fbadee955..ffe09475ee 100644
--- a/src/calibre/utils/fonts/subset.py
+++ b/src/calibre/utils/fonts/subset.py
@@ -110,13 +110,18 @@ def test():
 def all():
     from calibre.utils.fonts.scanner import font_scanner
     failed = []
+    unsupported = []
     for family in font_scanner.find_font_families():
         for font in font_scanner.fonts_for_family(family):
             raw = font_scanner.get_font_data(font)
-            print ('Subsetting', font['full_name'])
+            print ('Subsetting', font['full_name'], end='\t')
             try:
                 sf, old_stats, new_stats = subset(raw, set(('a', 'b', 'c')), ())
-            except (NoGlyphs, UnsupportedFont) as e:
+            except NoGlyphs:
+                continue
+            except UnsupportedFont as e:
+                unsupported.append((font['full_name'], font['path'], unicode(e)))
+                print ('Unsupported!')
                 continue
             except Exception as e:
                 print ('Failed!')
@@ -125,6 +130,11 @@ def all():
                 print ('Reduced to:', '%.1f'%(
                         sum(new_stats.itervalues())/sum(old_stats.itervalues())
                         * 100), '%')
+    if unsupported:
+        print ('\n\nUnsupported:')
+        for name, path, err in unsupported:
+            print (name, path, err)
+            print()
     if failed:
         print ('\n\nFailures:')
         for name, path, err in failed: