diff --git a/src/plugins/clangcodemodel/clangdclient.cpp b/src/plugins/clangcodemodel/clangdclient.cpp
index f0637feb753..894f22aaa92 100644
--- a/src/plugins/clangcodemodel/clangdclient.cpp
+++ b/src/plugins/clangcodemodel/clangdclient.cpp
@@ -1321,7 +1321,12 @@ ClangdClient::ClangdClient(Project *project, const Utils::FilePath &jsonDbDir)
         return new ClangdTextMark(filePath, diag, isProjectFile, this);
     };
     const auto hideDiagsHandler = []{ ClangDiagnosticManager::clearTaskHubIssues(); };
-    setDiagnosticsHandlers(textMarkCreator, hideDiagsHandler);
+    static const auto diagsFilter = [](const Diagnostic &diag) {
+        const Diagnostic::Code code = diag.code().value_or(Diagnostic::Code());
+        const QString * const codeString = Utils::get_if<QString>(&code);
+        return !codeString || *codeString != "drv_unknown_argument";
+    };
+    setDiagnosticsHandlers(textMarkCreator, hideDiagsHandler, diagsFilter);
     setSymbolStringifier(displayNameFromDocumentSymbol);
     setSemanticTokensHandler([this](TextDocument *doc, const QList<ExpandedSemanticToken> &tokens,
                                     int version, bool force) {
diff --git a/src/plugins/clangcodemodel/test/data/completion/completion.pro b/src/plugins/clangcodemodel/test/data/completion/completion.pro
index da641f22378..832b9aac07f 100644
--- a/src/plugins/clangcodemodel/test/data/completion/completion.pro
+++ b/src/plugins/clangcodemodel/test/data/completion/completion.pro
@@ -27,5 +27,7 @@ SOURCES = \
     privateFuncDefCompletion.cpp \
     signalCompletion.cpp
 
+QMAKE_CXXFLAGS += -ffoo
+
 HEADERS = mainwindow.h
 FORMS = mainwindow.ui
diff --git a/src/plugins/clangcodemodel/test/data/find-usages/find-usages.pro b/src/plugins/clangcodemodel/test/data/find-usages/find-usages.pro
index c4474855308..cf511fee40a 100644
--- a/src/plugins/clangcodemodel/test/data/find-usages/find-usages.pro
+++ b/src/plugins/clangcodemodel/test/data/find-usages/find-usages.pro
@@ -2,3 +2,4 @@ TEMPLATE = app
 QT = core
 HEADERS = defs.h
 SOURCES = main.cpp
+QMAKE_CXXFLAGS += -ffoo
diff --git a/src/plugins/clangcodemodel/test/data/follow-symbol/follow-symbol.pro b/src/plugins/clangcodemodel/test/data/follow-symbol/follow-symbol.pro
index 7d2c3147a3e..8b0d6d1879b 100644
--- a/src/plugins/clangcodemodel/test/data/follow-symbol/follow-symbol.pro
+++ b/src/plugins/clangcodemodel/test/data/follow-symbol/follow-symbol.pro
@@ -2,3 +2,4 @@ TEMPLATE = app
 CONFIG -= qt
 HEADERS = cursor.h header.h
 SOURCES = cursor.cpp main.cpp
+QMAKE_CXXFLAGS += -ffoo
diff --git a/src/plugins/clangcodemodel/test/data/highlighting/highlighting.pro b/src/plugins/clangcodemodel/test/data/highlighting/highlighting.pro
index 7dd57583ea9..32196b9724f 100644
--- a/src/plugins/clangcodemodel/test/data/highlighting/highlighting.pro
+++ b/src/plugins/clangcodemodel/test/data/highlighting/highlighting.pro
@@ -1,3 +1,4 @@
 TEMPLATE = app
 CONFIG -= qt
 SOURCES = highlighting.cpp
+QMAKE_CXXFLAGS += -ffoo
diff --git a/src/plugins/clangcodemodel/test/data/local-references/local-references.pro b/src/plugins/clangcodemodel/test/data/local-references/local-references.pro
index c3b335aad8d..f47c1c68154 100644
--- a/src/plugins/clangcodemodel/test/data/local-references/local-references.pro
+++ b/src/plugins/clangcodemodel/test/data/local-references/local-references.pro
@@ -1,5 +1,4 @@
 TEMPLATE = app
-
 CONFIG -= qt
-
 SOURCES = references.cpp
+QMAKE_CXXFLAGS += -ffoo
diff --git a/src/plugins/languageclient/client.cpp b/src/plugins/languageclient/client.cpp
index 79a6782e060..541ba0d3e21 100644
--- a/src/plugins/languageclient/client.cpp
+++ b/src/plugins/languageclient/client.cpp
@@ -1054,9 +1054,10 @@ bool Client::hasDiagnostic(const LanguageServerProtocol::DocumentUri &uri,
 }
 
 void Client::setDiagnosticsHandlers(const TextMarkCreator &textMarkCreator,
-                                    const HideDiagnosticsHandler &hideHandler)
+                                    const HideDiagnosticsHandler &hideHandler,
+                                    const DiagnosticsFilter &filter)
 {
-    m_diagnosticManager.setDiagnosticsHandlers(textMarkCreator, hideHandler);
+    m_diagnosticManager.setDiagnosticsHandlers(textMarkCreator, hideHandler, filter);
 }
 
 void Client::setSemanticTokensHandler(const SemanticTokensHandler &handler)
diff --git a/src/plugins/languageclient/client.h b/src/plugins/languageclient/client.h
index d95d5693609..f1e9c581f48 100644
--- a/src/plugins/languageclient/client.h
+++ b/src/plugins/languageclient/client.h
@@ -186,7 +186,7 @@ public:
     bool hasDiagnostic(const LanguageServerProtocol::DocumentUri &uri,
                        const LanguageServerProtocol::Diagnostic &diag) const;
     void setDiagnosticsHandlers(const TextMarkCreator &textMarkCreator,
-                                const HideDiagnosticsHandler &hideHandler);
+                                const HideDiagnosticsHandler &hideHandler, const DiagnosticsFilter &filter);
     void setSemanticTokensHandler(const SemanticTokensHandler &handler);
     void setSymbolStringifier(const LanguageServerProtocol::SymbolStringifier &stringifier);
     LanguageServerProtocol::SymbolStringifier symbolStringifier() const;
diff --git a/src/plugins/languageclient/diagnosticmanager.cpp b/src/plugins/languageclient/diagnosticmanager.cpp
index 2b1d66c477d..a1b729ce9bf 100644
--- a/src/plugins/languageclient/diagnosticmanager.cpp
+++ b/src/plugins/languageclient/diagnosticmanager.cpp
@@ -90,7 +90,9 @@ void DiagnosticManager::setDiagnostics(const LanguageServerProtocol::DocumentUri
                                        const Utils::optional<int> &version)
 {
     hideDiagnostics(uri.toFilePath());
-    m_diagnostics[uri] = {version, diagnostics};
+    const QList<Diagnostic> filteredDiags = m_filter
+            ? Utils::filtered(diagnostics, m_filter) : diagnostics;
+    m_diagnostics[uri] = {version, filteredDiags};
 }
 
 void DiagnosticManager::hideDiagnostics(const Utils::FilePath &filePath)
@@ -201,10 +203,12 @@ bool DiagnosticManager::hasDiagnostic(const LanguageServerProtocol::DocumentUri
 }
 
 void DiagnosticManager::setDiagnosticsHandlers(const TextMarkCreator &textMarkCreator,
-                                               const HideDiagnosticsHandler &removalHandler)
+                                               const HideDiagnosticsHandler &removalHandler,
+                                               const DiagnosticsFilter &filter)
 {
     m_textMarkCreator = textMarkCreator;
     m_hideHandler = removalHandler;
+    m_filter = filter;
 }
 
 } // namespace LanguageClient
diff --git a/src/plugins/languageclient/diagnosticmanager.h b/src/plugins/languageclient/diagnosticmanager.h
index c4bfabf71a3..f201aaf50c2 100644
--- a/src/plugins/languageclient/diagnosticmanager.h
+++ b/src/plugins/languageclient/diagnosticmanager.h
@@ -45,6 +45,7 @@ class Client;
 using TextMarkCreator = std::function<TextEditor::TextMark *(const Utils::FilePath &,
         const LanguageServerProtocol::Diagnostic &, bool)>;
 using HideDiagnosticsHandler = std::function<void()>;
+using DiagnosticsFilter = std::function<bool(const LanguageServerProtocol::Diagnostic &)>;
 
 class DiagnosticManager
 {
@@ -70,7 +71,8 @@ public:
                        const LanguageServerProtocol::Diagnostic &diag) const;
 
     void setDiagnosticsHandlers(const TextMarkCreator &shownHandler,
-                                const HideDiagnosticsHandler &removalHandler);
+                                const HideDiagnosticsHandler &removalHandler,
+                                const DiagnosticsFilter &filter);
 
 private:
     TextEditor::TextMark *createTextMark(const Utils::FilePath &filePath,
@@ -83,6 +85,7 @@ private:
     QMap<Utils::FilePath, QList<TextEditor::TextMark *>> m_marks;
     TextMarkCreator m_textMarkCreator;
     HideDiagnosticsHandler m_hideHandler;
+    DiagnosticsFilter m_filter;
     Client *m_client;
 };