diff --git a/src/plugins/projectexplorer/gcctoolchain.cpp b/src/plugins/projectexplorer/gcctoolchain.cpp
index 78b5ba4737a..8a39318aaea 100644
--- a/src/plugins/projectexplorer/gcctoolchain.cpp
+++ b/src/plugins/projectexplorer/gcctoolchain.cpp
@@ -48,6 +48,49 @@ using namespace Utils;
 namespace ProjectExplorer {
 namespace Internal {
 
+class WarningFlagAdder
+{
+public:
+    WarningFlagAdder(const QString &flag, WarningFlags &flags) :
+        m_flags(flags)
+    {
+        if (!flag.startsWith("-W")) {
+            m_triggered = true;
+            return;
+        }
+
+        m_doesEnable = !flag.startsWith("-Wno-");
+        if (m_doesEnable)
+            m_flagUtf8 = flag.mid(2).toUtf8();
+        else
+            m_flagUtf8 = flag.mid(5).toUtf8();
+    }
+
+    void operator()(const char name[], WarningFlags flagsSet)
+    {
+        if (m_triggered)
+            return;
+        if (0 == strcmp(m_flagUtf8.data(), name)) {
+            m_triggered = true;
+            if (m_doesEnable)
+                m_flags |= flagsSet;
+            else
+                m_flags &= ~flagsSet;
+        }
+    }
+
+    bool triggered() const
+    {
+        return m_triggered;
+    }
+
+private:
+    QByteArray m_flagUtf8;
+    WarningFlags &m_flags;
+    bool m_doesEnable = false;
+    bool m_triggered = false;
+};
+
 static const QStringList languageOption(Id languageId)
 {
     if (languageId == Constants::C_LANGUAGE_ID)
@@ -1975,40 +2018,6 @@ void GccToolChainConfigWidget::updateParentToolChainComboBox()
     }
 }
 
-GccToolChain::WarningFlagAdder::WarningFlagAdder(const QString &flag, WarningFlags &flags) :
-    m_flags(flags)
-{
-    if (!flag.startsWith("-W")) {
-        m_triggered = true;
-        return;
-    }
-
-    m_doesEnable = !flag.startsWith("-Wno-");
-    if (m_doesEnable)
-        m_flagUtf8 = flag.mid(2).toUtf8();
-    else
-        m_flagUtf8 = flag.mid(5).toUtf8();
-}
-
-void GccToolChain::WarningFlagAdder::operator ()(const char name[], WarningFlags flagsSet)
-{
-    if (m_triggered)
-        return;
-    if (0 == strcmp(m_flagUtf8.data(), name))
-    {
-        m_triggered = true;
-        if (m_doesEnable)
-            m_flags |= flagsSet;
-        else
-            m_flags &= ~flagsSet;
-    }
-}
-
-bool GccToolChain::WarningFlagAdder::triggered() const
-{
-    return m_triggered;
-}
-
 } // namespace ProjectExplorer
 
 // Unit tests:
diff --git a/src/plugins/projectexplorer/gcctoolchain.h b/src/plugins/projectexplorer/gcctoolchain.h
index 207d93f5bd8..52ffabc839b 100644
--- a/src/plugins/projectexplorer/gcctoolchain.h
+++ b/src/plugins/projectexplorer/gcctoolchain.h
@@ -127,20 +127,6 @@ protected:
 
     int priority() const override { return m_priority; }
 
-    class WarningFlagAdder
-    {
-    public:
-        WarningFlagAdder(const QString &flag, Utils::WarningFlags &flags);
-        void operator ()(const char name[], Utils::WarningFlags flagsSet);
-
-        bool triggered() const;
-    private:
-        QByteArray m_flagUtf8;
-        Utils::WarningFlags &m_flags;
-        bool m_doesEnable = false;
-        bool m_triggered = false;
-    };
-
     QString sysRoot() const override;
 
 private: