diff --git a/src/libs/cplusplus/CppDocument.cpp b/src/libs/cplusplus/CppDocument.cpp
index 80476dd8b1e..93f3654e4fb 100644
--- a/src/libs/cplusplus/CppDocument.cpp
+++ b/src/libs/cplusplus/CppDocument.cpp
@@ -286,8 +286,10 @@ Document::~Document()
 {
     delete _translationUnit;
     _translationUnit = 0;
-    delete _control->diagnosticClient();
-    delete _control;
+    if (_control) {
+        delete _control->diagnosticClient();
+        delete _control;
+    }
     _control = 0;
 }
 
@@ -296,6 +298,25 @@ Control *Document::control() const
     return _control;
 }
 
+Control *Document::swapControl(Control *newControl)
+{
+    if (newControl) {
+        const StringLiteral *fileId = newControl->stringLiteral(_translationUnit->fileId()->chars(),
+                                                                _translationUnit->fileId()->size());
+        const auto newTranslationUnit = new TranslationUnit(newControl, fileId);
+        newTranslationUnit->setLanguageFeatures(_translationUnit->languageFeatures());
+        delete _translationUnit;
+        _translationUnit = newTranslationUnit;
+    } else {
+        delete _translationUnit;
+        _translationUnit = 0;
+    }
+
+    Control *oldControl = _control;
+    _control = newControl;
+    return oldControl;
+}
+
 unsigned Document::revision() const
 {
     return _revision;
@@ -696,7 +717,8 @@ void Document::releaseSourceAndAST()
     if (!_keepSourceAndASTCount.deref()) {
         _source.clear();
         _translationUnit->release();
-        _control->squeeze();
+        if (_control)
+            _control->squeeze();
     }
 }
 
diff --git a/src/libs/cplusplus/CppDocument.h b/src/libs/cplusplus/CppDocument.h
index bac2fb2a472..006f17aba68 100644
--- a/src/libs/cplusplus/CppDocument.h
+++ b/src/libs/cplusplus/CppDocument.h
@@ -78,6 +78,7 @@ public:
                               unsigned bytesOffset, unsigned utf16charsOffset);
 
     Control *control() const;
+    Control *swapControl(Control *newControl);
     TranslationUnit *translationUnit() const;
 
     bool skipFunctionBody() const;
diff --git a/src/libs/cplusplus/ResolveExpression.cpp b/src/libs/cplusplus/ResolveExpression.cpp
index 2f55c1564f2..69ce4f4cb4e 100644
--- a/src/libs/cplusplus/ResolveExpression.cpp
+++ b/src/libs/cplusplus/ResolveExpression.cpp
@@ -688,6 +688,31 @@ public:
     bool _block;
 };
 
+class ExpressionDocumentHelper
+{
+public:
+    // Set up an expression document with an external Control
+    ExpressionDocumentHelper(const QByteArray &utf8code, Control *control)
+        : document(Document::create(QLatin1String("<completion>")))
+    {
+        Control *oldControl = document->swapControl(control);
+        delete oldControl->diagnosticClient();
+        delete oldControl;
+        document->setUtf8Source(utf8code);
+        document->parse(Document::ParseExpression);
+        document->check();
+    }
+
+    // Ensure that the external Control is not deleted
+    ~ExpressionDocumentHelper()
+    {
+        document->swapControl(nullptr);
+    }
+
+public:
+    Document::Ptr document;
+};
+
 } // namespace anonymous
 
 bool ResolveExpression::visit(SimpleNameAST *ast)
@@ -730,9 +755,9 @@ bool ResolveExpression::visit(SimpleNameAST *ast)
             exprTyper.init(doc, _context.snapshot(), _context.bindings(),
                            QSet<const Declaration* >(_autoDeclarationsBeingResolved) << decl);
 
-            Document::Ptr exprDoc =
-                    documentForExpression(exprTyper.preprocessedExpression(initializer));
-            exprDoc->check();
+            const ExpressionDocumentHelper exprHelper(exprTyper.preprocessedExpression(initializer),
+                                                      _context.bindings()->control().data());
+            const Document::Ptr exprDoc = exprHelper.document;
 
             DeduceAutoCheck deduceAuto(ast->name->identifier(), exprDoc->translationUnit());
             if (deduceAuto._block)