diff --git a/src/pyj/book_list/boss.pyj b/src/pyj/book_list/boss.pyj
index a82b327f02..adcbfbb9f0 100644
--- a/src/pyj/book_list/boss.pyj
+++ b/src/pyj/book_list/boss.pyj
@@ -19,9 +19,13 @@ class Boss:
         document.title = 'calibre :: ' + self.current_library_name
 
     def onerror(self, msg, script_url, line_number, column_number, error_object):
-        fname = str.rpartition(script_url, '/')[-1] or script_url
-        msg = msg + '<br><span style="font-size:smaller">' + str.format('Error at {}:{}:{}', fname, line_number, column_number or '') + '</span>'
-        details = ''
-        if error_object and error_object.stack:
-            details = error_object.stack
-        error_dialog(_('Unhandled error'), msg, details)
+        try:
+            fname = str.rpartition(script_url, '/')[-1] or script_url
+            msg = msg + '<br><span style="font-size:smaller">' + str.format('Error at {}:{}:{}', fname, line_number, column_number or '') + '</span>'
+            details = ''
+            if error_object and error_object.stack:
+                details = error_object.stack
+            error_dialog(_('Unhandled error'), msg, details)
+            return True
+        except:
+            console.error('There was an error in the unhandled exception handler')