diff --git a/orangecontrib/text/widgets/owcorpusviewer.py b/orangecontrib/text/widgets/owcorpusviewer.py
index ef18fdaef..775ddba67 100644
--- a/orangecontrib/text/widgets/owcorpusviewer.py
+++ b/orangecontrib/text/widgets/owcorpusviewer.py
@@ -23,6 +23,7 @@
     QSizePolicy,
     QSplitter,
     QTableView,
+    QMessageBox,
 )
 from Orange.data import Variable
 from Orange.data.domain import Domain, filter_visible
@@ -115,7 +116,7 @@
 )
 
 
-def _count_matches(content: List[str], search_string: str, state: TaskState) -> int:
+def _count_matches(content: List[str], regex: re.Pattern, state: TaskState) -> int:
     """
     Count number of appears of any terms in search_string in content texts.
 
@@ -132,8 +133,7 @@ def _count_matches(content: List[str], search_string: str, state: TaskState) ->
     Number of all matches of search_string in all texts in content list
     """
     matches = 0
-    if search_string:
-        regex = re.compile(search_string.strip("|"), re.IGNORECASE)
+    if regex.pattern:
         for i, text in enumerate(content):
             matches += len(regex.findall(text))
             state.set_progress_value((i + 1) / len(content) * 100)
@@ -186,6 +186,10 @@ class DocumentsFilterProxyModel(QSortFilterProxyModel):
     __regex = None
 
     def set_filter_string(self, filter_string: str):
+        try:
+            re.compile(filter_string.strip("|"), re.IGNORECASE)
+        except re.error:
+            return
         self.__regex = re.compile(filter_string.strip("|"), re.IGNORECASE)
         self.invalidateFilter()
 
@@ -313,6 +317,9 @@ class Outputs:
     class Warning(OWWidget.Warning):
         no_feats_search = Msg("No features included in search.")
         no_feats_display = Msg("No features selected for display.")
+        
+    class Error(OWWidget.Error):
+        invalid_regex = Msg("Invalid regular expression.")
 
     def __init__(self):
         super().__init__()
@@ -587,6 +594,7 @@ def regenerate_docs(self) -> List[str]:
         return self.corpus.documents_from_features(self.search_features)
 
     def refresh_search(self):
+        self.Error.invalid_regex.clear()
         if self.corpus is not None:
             self.doc_list.model().set_filter_string(self.regexp_filter)
             if not self.selected_documents:
@@ -594,11 +602,21 @@ def refresh_search(self):
                 # select first element in the view in that case
                 self.doc_list.setCurrentIndex(self.doc_list.model().index(0, 0))
             self.update_info()
-            self.start(
-                _count_matches,
-                self.doc_list_model.get_filter_content(),
-                self.regexp_filter,
-            )
+            try:
+                self.compiled_regex = re.compile(self.regexp_filter.strip("|"), re.IGNORECASE)
+                self.start(
+                    _count_matches,
+                    self.doc_list_model.get_filter_content(),
+                    self.compiled_regex,
+                )
+            except re.error:
+                self.Error.invalid_regex()
+                self.compiled_regex = None 
+                self.n_matching = "n/a"
+                self.n_matches = "n/a"
+                self.n_tokens = "n/a"
+                self.n_types = "n/a"
+                
             self.show_docs()
             self.commit.deferred()
 
diff --git a/orangecontrib/text/widgets/tests/test_owcorpusviewer.py b/orangecontrib/text/widgets/tests/test_owcorpusviewer.py
index 0abdcbbdc..4b22c6365 100644
--- a/orangecontrib/text/widgets/tests/test_owcorpusviewer.py
+++ b/orangecontrib/text/widgets/tests/test_owcorpusviewer.py
@@ -140,6 +140,20 @@ def test_search(self):
         self.wait_until_finished()
         self.assertEqual(self.widget.n_matches, 0)
 
+    def test_invalid_regex(self):
+        # Error is shown when invalid regex is entered
+        self.send_signal(self.widget.Inputs.corpus, self.corpus)
+        self.widget.regexp_filter = "*"
+        self.widget.refresh_search()
+        self.process_events()
+        self.assertEqual(self.widget.n_matches, "n/a")
+        self.assertTrue(self.widget.Error.invalid_regex.is_shown())
+        # Error is hidden when valid regex is entered
+        self.widget.regexp_filter = "graph"
+        self.widget.refresh_search()
+        self.process_events()
+        self.assertFalse(self.widget.Error.invalid_regex.is_shown())      
+   
     def test_highlighting(self):
         self.send_signal(self.widget.Inputs.corpus, self.corpus)
         # no intersection between filter and selection