diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index a99761940c..a9e6ecc6ae 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -690,21 +690,21 @@ class Boss(QObject):
 
         def do_find():
             if editor is not None:
-                if editor.find(pat, marked=marked):
+                if editor.find(pat, marked=marked, save_match='gui'):
                     return
                 if not files:
                     if not state['wrap']:
                         return no_match()
-                    return editor.find(pat, wrap=True, marked=marked) or no_match()
+                    return editor.find(pat, wrap=True, marked=marked, save_match='gui') or no_match()
             for fname, syntax in files.iteritems():
                 if fname in editors:
-                    if not editors[fname].find(pat, complete=True):
+                    if not editors[fname].find(pat, complete=True, save_match='gui'):
                         continue
                     return self.show_editor(fname)
                 raw = current_container().raw_data(fname)
                 if pat.search(raw) is not None:
                     self.edit_file(fname, syntax)
-                    if editors[fname].find(pat, complete=True):
+                    if editors[fname].find(pat, complete=True, save_match='gui'):
                         return
             return no_match()
 
@@ -720,7 +720,7 @@ class Boss(QObject):
         def do_replace():
             if editor is None:
                 return no_replace()
-            if not editor.replace(pat, state['replace']):
+            if not editor.replace(pat, state['replace'], saved_match='gui'):
                 return no_replace(_(
                         'Currently selected text does not match the search query.'))
             return True
diff --git a/src/calibre/gui2/tweak_book/editor/text.py b/src/calibre/gui2/tweak_book/editor/text.py
index d86db05044..be3fb8aae6 100644
--- a/src/calibre/gui2/tweak_book/editor/text.py
+++ b/src/calibre/gui2/tweak_book/editor/text.py
@@ -115,6 +115,7 @@ class TextEdit(PlainTextEdit):
 
     def __init__(self, parent=None):
         PlainTextEdit.__init__(self, parent)
+        self.saved_matches = {}
         self.smarts = NullSmarts(self)
         self.current_cursor_line = None
         self.current_search_mark = None
@@ -256,7 +257,7 @@ class TextEdit(PlainTextEdit):
             self.current_search_mark = None
         self.update_extra_selections()
 
-    def find_in_marked(self, pat, wrap=False):
+    def find_in_marked(self, pat, wrap=False, save_match=None):
         if self.current_search_mark is None:
             return False
         csm = self.current_search_mark.cursor
@@ -298,6 +299,8 @@ class TextEdit(PlainTextEdit):
         self.setTextCursor(c)
         # Center search result on screen
         self.centerCursor()
+        if save_match is not None:
+            self.saved_matches[save_match] = m
         return True
 
     def all_in_marked(self, pat, template=None):
@@ -316,9 +319,9 @@ class TextEdit(PlainTextEdit):
                 self.update_extra_selections()
         return count
 
-    def find(self, pat, wrap=False, marked=False, complete=False):
+    def find(self, pat, wrap=False, marked=False, complete=False, save_match=None):
         if marked:
-            return self.find_in_marked(pat, wrap=wrap)
+            return self.find_in_marked(pat, wrap=wrap, save_match=save_match)
         reverse = pat.flags & regex.REVERSE
         c = self.textCursor()
         c.clearSelection()
@@ -353,12 +356,23 @@ class TextEdit(PlainTextEdit):
         self.setTextCursor(c)
         # Center search result on screen
         self.centerCursor()
+        if save_match is not None:
+            self.saved_matches[save_match] = m
         return True
 
-    def replace(self, pat, template):
+    def replace(self, pat, template, saved_match='gui'):
         c = self.textCursor()
         raw = unicode(c.selectedText()).replace(PARAGRAPH_SEPARATOR, '\n')
         m = pat.fullmatch(raw)
+        if m is None:
+            # This can happen if either the user changed the selected text or
+            # the search expression uses lookahead/lookbehind operators. See if
+            # the saved match matches the currently selected text and
+            # use it, if so.
+            if saved_match is not None and saved_match in self.saved_matches:
+                saved = self.saved_matches.pop(saved_match)
+                if saved.group() == raw:
+                    m = saved
         if m is None:
             return False
         text = m.expand(template)