diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index 9f350008c7..c52109cbf8 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -676,6 +676,9 @@ class Boss(QObject):
         self.gui.action_save.setEnabled(True)
 
     def request_completion(self, name, completion_type, completion_data, query=None):
+        if completion_type is None:
+            completion_worker().clear_caches(completion_data)
+            return
         request_id = (self.completion_request_count, name)
         self.completion_request_count += 1
         completion_worker().queue_completion(request_id, completion_type, completion_data, query)
diff --git a/src/calibre/gui2/tweak_book/completion/basic.py b/src/calibre/gui2/tweak_book/completion/basic.py
index 8831fbd382..4326da4827 100644
--- a/src/calibre/gui2/tweak_book/completion/basic.py
+++ b/src/calibre/gui2/tweak_book/completion/basic.py
@@ -22,12 +22,19 @@ from calibre.utils.matcher import Matcher
 Request = namedtuple('Request', 'id type data query')
 
 names_cache = {}
+file_cache = {}
 
 @control
 def clear_caches(cache_type, data_conn):
-    global names_cache
-    if cache_type is None or cache_type == 'names':
+    global names_cache, file_cache
+    if cache_type is None:
         names_cache.clear()
+        file_cache.clear()
+        return
+    if cache_type == 'names':
+        names_cache.clear()
+    elif cache_type.startswith('file:'):
+        file_cache.pop(cache_type.partition(':')[2], None)
 
 @data
 def names_data(request_data):
diff --git a/src/calibre/gui2/tweak_book/editor/smarts/html.py b/src/calibre/gui2/tweak_book/editor/smarts/html.py
index 46067f2583..fa0559e903 100644
--- a/src/calibre/gui2/tweak_book/editor/smarts/html.py
+++ b/src/calibre/gui2/tweak_book/editor/smarts/html.py
@@ -642,7 +642,7 @@ class Smarts(NullSmarts):
         if m is None:
             return
         attr = m.group(1).lower().split(':')[-1]
-        doc_name = editor.highlighter.doc_name
+        doc_name = editor.completion_doc_name
         if doc_name and attr in {'href', 'src'}:
             # A link
             query = m.group(2) or m.group(3) or ''
diff --git a/src/calibre/gui2/tweak_book/editor/text.py b/src/calibre/gui2/tweak_book/editor/text.py
index 6f453744b1..390d5eaae0 100644
--- a/src/calibre/gui2/tweak_book/editor/text.py
+++ b/src/calibre/gui2/tweak_book/editor/text.py
@@ -141,6 +141,9 @@ class TextEdit(PlainTextEdit):
         PlainTextEdit.__init__(self, parent)
         self.completion_popup = CompletionPopup(self)
         self.request_completion = self.completion_doc_name = None
+        self.clear_completion_cache_timer = t = QTimer(self)
+        t.setInterval(5000), t.timeout.connect(self.clear_completion_cache), t.setSingleShot(True)
+        self.textChanged.connect(t.start)
         self.last_completion_request = -1
         self.gutter_width = 0
         self.tw = 2
@@ -803,6 +806,10 @@ class TextEdit(PlainTextEdit):
         if result.request_id[0] >= self.last_completion_request:
             self.completion_popup.handle_result(result)
 
+    def clear_completion_cache(self):
+        if self.request_completion is not None and self.completion_doc_name:
+            self.request_completion(None, 'file:' + self.completion_doc_name)
+
     def replace_possible_unicode_sequence(self):
         c = self.textCursor()
         has_selection = c.hasSelection()