diff --git a/src/plugins/cpptools/cppcodemodelsettings.cpp b/src/plugins/cpptools/cppcodemodelsettings.cpp
index 5aaaa2c105a..b7ebb1ddaa0 100644
--- a/src/plugins/cpptools/cppcodemodelsettings.cpp
+++ b/src/plugins/cpptools/cppcodemodelsettings.cpp
@@ -118,6 +118,12 @@ void CppCodeModelSettings::fromSettings(QSettings *s)
     setClangCustomDiagnosticConfigs(customDiagnosticConfigsFromSettings(s));
     setClangDiagnosticConfigId(clangDiagnosticConfigIdFromSettings(s));
 
+    { // Before Qt Creator 4.8, inconsistent settings might have been written.
+        const ClangDiagnosticConfigsModel model(m_clangCustomDiagnosticConfigs);
+        if (!model.hasConfigWithId(m_clangDiagnosticConfigId))
+            setClangDiagnosticConfigId(initialClangDiagnosticConfigId());
+    }
+
     const QVariant pchUsageVariant = s->value(pchUsageKey(), initialPchUsage());
     setPCHUsage(static_cast<PCHUsage>(pchUsageVariant.toInt()));