diff --git a/src/plugins/clangcodemodel/clangeditordocumentparser.cpp b/src/plugins/clangcodemodel/clangeditordocumentparser.cpp
index e12833ca9a1..9b342bd7d1a 100644
--- a/src/plugins/clangcodemodel/clangeditordocumentparser.cpp
+++ b/src/plugins/clangcodemodel/clangeditordocumentparser.cpp
@@ -94,7 +94,7 @@ void ClangEditorDocumentParser::update(CppTools::WorkingCopy workingCopy)
     QMutexLocker lock(m_marker->mutex());
     QMutexLocker lock2(&m_mutex);
 
-    updateProjectPart();
+    m_projectPart = determineProjectPart();
     const QStringList options = createOptions(filePath(), projectPart(), true);
 
     qCDebug(log, "Reparse options (cmd line equivalent): %s",
diff --git a/src/plugins/cpptools/baseeditordocumentparser.cpp b/src/plugins/cpptools/baseeditordocumentparser.cpp
index 7f1e74785b1..d24e341b1f2 100644
--- a/src/plugins/cpptools/baseeditordocumentparser.cpp
+++ b/src/plugins/cpptools/baseeditordocumentparser.cpp
@@ -45,7 +45,7 @@ namespace CppTools {
     the "best" project part for a file.
 
     Derived classes are expected to implement update() by using the protected
-    mutex, updateProjectPart() and by respecting the options set by the client.
+    mutex, determineProjectPart() and by respecting the options set by the client.
 */
 
 BaseEditorDocumentParser::BaseEditorDocumentParser(const QString &filePath)
@@ -115,33 +115,35 @@ BaseEditorDocumentParser *BaseEditorDocumentParser::get(const QString &filePath)
     return 0;
 }
 
-void BaseEditorDocumentParser::updateProjectPart()
+ProjectPart::Ptr BaseEditorDocumentParser::determineProjectPart() const
 {
-    if (m_manuallySetProjectPart) {
-        m_projectPart = m_manuallySetProjectPart;
-        return;
-    }
+    if (m_manuallySetProjectPart)
+        return m_manuallySetProjectPart;
+
+    ProjectPart::Ptr projectPart = m_projectPart;
 
     CppModelManager *cmm = CppModelManager::instance();
     QList<ProjectPart::Ptr> projectParts = cmm->projectPart(m_filePath);
     if (projectParts.isEmpty()) {
-        if (m_projectPart)
+        if (projectPart)
             // File is not directly part of any project, but we got one before. We will re-use it,
             // because re-calculating this can be expensive when the dependency table is big.
-            return;
+            return projectPart;
 
         // Fall-back step 1: Get some parts through the dependency table:
         projectParts = cmm->projectPartFromDependencies(Utils::FileName::fromString(m_filePath));
         if (projectParts.isEmpty())
             // Fall-back step 2: Use fall-back part from the model manager:
-            m_projectPart = cmm->fallbackProjectPart();
+            projectPart = cmm->fallbackProjectPart();
         else
-            m_projectPart = projectParts.first();
+            projectPart = projectParts.first();
     } else {
-        if (!projectParts.contains(m_projectPart))
+        if (!projectParts.contains(projectPart))
             // Apparently the project file changed, so update our project part.
-            m_projectPart = projectParts.first();
+            projectPart = projectParts.first();
     }
+
+    return projectPart;
 }
 
 bool BaseEditorDocumentParser::editorDefinesChanged() const
diff --git a/src/plugins/cpptools/baseeditordocumentparser.h b/src/plugins/cpptools/baseeditordocumentparser.h
index ddd12fbb0aa..c8f5704a9dc 100644
--- a/src/plugins/cpptools/baseeditordocumentparser.h
+++ b/src/plugins/cpptools/baseeditordocumentparser.h
@@ -63,18 +63,18 @@ public:
     static BaseEditorDocumentParser *get(const QString &filePath);
 
 protected:
-    void updateProjectPart();
+    ProjectPart::Ptr determineProjectPart() const;
 
     bool editorDefinesChanged() const;
     void resetEditorDefinesChanged();
 
 protected:
     mutable QMutex m_mutex;
+    ProjectPart::Ptr m_projectPart;
 
 private:
     const QString m_filePath;
 
-    ProjectPart::Ptr m_projectPart;
     ProjectPart::Ptr m_manuallySetProjectPart;
 
     bool m_usePrecompiledHeaders;
diff --git a/src/plugins/cpptools/builtineditordocumentparser.cpp b/src/plugins/cpptools/builtineditordocumentparser.cpp
index 24ae027bfc4..8c2232f1422 100644
--- a/src/plugins/cpptools/builtineditordocumentparser.cpp
+++ b/src/plugins/cpptools/builtineditordocumentparser.cpp
@@ -62,7 +62,7 @@ void BuiltinEditorDocumentParser::update(WorkingCopy workingCopy)
     QString projectConfigFile;
     LanguageFeatures features = LanguageFeatures::defaultFeatures();
 
-    updateProjectPart();
+    m_projectPart = determineProjectPart();
 
     if (m_forceSnapshotInvalidation) {
         invalidateSnapshot = true;