diff --git a/src/plugins/clangtools/clangtidyclazytool.cpp b/src/plugins/clangtools/clangtidyclazytool.cpp
index cf4a4ea5a46..575cd68dc5b 100644
--- a/src/plugins/clangtools/clangtidyclazytool.cpp
+++ b/src/plugins/clangtools/clangtidyclazytool.cpp
@@ -395,7 +395,7 @@ void ClangTidyClazyTool::handleStateUpdate()
     QTC_ASSERT(m_diagnosticModel, return);
     QTC_ASSERT(m_diagnosticFilterModel, return);
 
-    const int issuesFound = m_diagnosticModel->diagnostics().count();
+    const int issuesFound = m_diagnosticModel->diagnosticsCount();
     const int issuesVisible = m_diagnosticFilterModel->rowCount();
     m_goBack->setEnabled(issuesVisible > 1);
     m_goNext->setEnabled(issuesVisible > 1);
diff --git a/src/plugins/clangtools/clangtoolsdiagnosticmodel.cpp b/src/plugins/clangtools/clangtoolsdiagnosticmodel.cpp
index db7ab4e14a2..690f48e584d 100644
--- a/src/plugins/clangtools/clangtoolsdiagnosticmodel.cpp
+++ b/src/plugins/clangtools/clangtoolsdiagnosticmodel.cpp
@@ -80,6 +80,11 @@ QList<Diagnostic> ClangToolsDiagnosticModel::diagnostics() const
     return diags;
 }
 
+int ClangToolsDiagnosticModel::diagnosticsCount() const
+{
+    return rootItem()->childCount();
+}
+
 static QString createDiagnosticToolTipString(const Diagnostic &diagnostic)
 {
     typedef QPair<QString, QString> StringPair;
@@ -431,8 +436,9 @@ bool DiagnosticFilterModel::filterAcceptsRow(int sourceRow,
         return true;
 
     // Is the diagnostic suppressed?
-    const Diagnostic diag = static_cast<ClangToolsDiagnosticModel *>(sourceModel())
-            ->diagnostics().at(sourceRow);
+    auto model = static_cast<ClangToolsDiagnosticModel *>(sourceModel());
+    auto item = static_cast<DiagnosticItem *>(model->rootItem()->childAt(sourceRow));
+    const Diagnostic &diag = item->diagnostic();
     foreach (const SuppressedDiagnostic &d, m_suppressedDiagnostics) {
         if (d.description != diag.description)
             continue;
diff --git a/src/plugins/clangtools/clangtoolsdiagnosticmodel.h b/src/plugins/clangtools/clangtoolsdiagnosticmodel.h
index 4c6a7e191c2..6ced6bfe22d 100644
--- a/src/plugins/clangtools/clangtoolsdiagnosticmodel.h
+++ b/src/plugins/clangtools/clangtoolsdiagnosticmodel.h
@@ -59,7 +59,7 @@ public:
     DiagnosticItem(const Diagnostic &diag, const OnFixitStatusChanged &onFixitStatusChanged);
     ~DiagnosticItem() override;
 
-    Diagnostic diagnostic() const { return m_diagnostic; }
+    const Diagnostic &diagnostic() const { return m_diagnostic; }
 
     FixitStatus fixItStatus() const { return m_fixitStatus; }
     void setFixItStatus(const FixitStatus &status);
@@ -90,6 +90,8 @@ public:
     virtual void addDiagnostics(const QList<Diagnostic> &diagnostics);
     virtual QList<Diagnostic> diagnostics() const;
 
+    int diagnosticsCount() const;
+
     enum ItemRole {
         DiagnosticRole = Debugger::DetailedErrorView::FullTextRole + 1
     };