diff --git a/src/calibre/gui2/tweak_book/file_list.py b/src/calibre/gui2/tweak_book/file_list.py
index 9d46c7ee6a..126f482678 100644
--- a/src/calibre/gui2/tweak_book/file_list.py
+++ b/src/calibre/gui2/tweak_book/file_list.py
@@ -13,9 +13,9 @@ from functools import partial
 from PyQt5.Qt import (
     QApplication, QCheckBox, QDialog, QDialogButtonBox, QFont, QFormLayout,
     QGridLayout, QIcon, QInputDialog, QLabel, QLineEdit, QListWidget,
-    QListWidgetItem, QMenu, QPainter, QPixmap, QRadioButton, QRawFont, QScrollArea,
-    QSize, QSpinBox, QStyle, QStyledItemDelegate, Qt, QTimer, QTreeWidget,
-    QTreeWidgetItem, QVBoxLayout, QWidget, pyqtSignal
+    QListWidgetItem, QMenu, QPainter, QPixmap, QRadioButton, QScrollArea, QSize,
+    QSpinBox, QStyle, QStyledItemDelegate, Qt, QTimer, QTreeWidget, QTreeWidgetItem,
+    QVBoxLayout, QWidget, pyqtSignal
 )
 
 from calibre import human_readable, plugins, sanitize_file_name
@@ -37,6 +37,7 @@ from calibre.gui2.tweak_book import (
 )
 from calibre.gui2.tweak_book.editor import syntax_from_mime
 from calibre.gui2.tweak_book.templates import template_for
+from calibre.utils.fonts.utils import get_font_names
 from calibre.utils.icu import numeric_sort_key
 from polyglot.binary import as_hex_unicode
 from polyglot.builtins import filter, iteritems, itervalues, map, range, unicode_type
@@ -468,7 +469,7 @@ class FileList(QTreeWidget):
                 # Duplicate entry in spine
                 emblems.append('dialog_error.png')
                 tooltips.append(_('This file occurs more than once in the spine'))
-            if category == 'fonts':
+            if category == 'fonts' and name.rpartition('.')[-1].lower() in ('ttf', 'otf'):
                 fname = self.get_font_family_name(name)
                 if fname:
                     tooltips.append(fname)
@@ -512,10 +513,9 @@ class FileList(QTreeWidget):
         key = name, sz
         if key not in self.font_name_cache:
             raw = current_container().raw_data(name, decode=False)
-            f = QRawFont(raw, 12)
-            if f.isValid():
-                ans = f.familyName() + ' ' + f.styleName()
-            else:
+            try:
+                ans = get_font_names(raw)[-1]
+            except Exception:
                 ans = None
             self.font_name_cache[key] = ans
         return self.font_name_cache[key]