diff --git a/src/plugins/languageclient/client.cpp b/src/plugins/languageclient/client.cpp
index e4923f3bc84..3d23d0cfb48 100644
--- a/src/plugins/languageclient/client.cpp
+++ b/src/plugins/languageclient/client.cpp
@@ -358,7 +358,7 @@ void Client::setClientCapabilities(const LanguageServerProtocol::ClientCapabilit
 void Client::openDocument(TextEditor::TextDocument *document)
 {
     using namespace TextEditor;
-    if (!isSupportedDocument(document))
+    if (m_openedDocument.contains(document) || !isSupportedDocument(document))
         return;
 
     if (m_state != Initialized) {
@@ -366,8 +366,6 @@ void Client::openDocument(TextEditor::TextDocument *document)
         return;
     }
 
-    QTC_ASSERT(!m_openedDocument.contains(document), return);
-
     const FilePath &filePath = document->filePath();
     const QString method(DidOpenTextDocumentNotification::methodName);
     if (Utils::optional<bool> registered = m_dynamicCapabilities.isRegistered(method)) {