diff --git a/src/plugins/qmljsinspector/qmljsdelta.cpp b/src/plugins/qmljsinspector/qmljsdelta.cpp
index 491571cd3d9..aa9d86827fb 100644
--- a/src/plugins/qmljsinspector/qmljsdelta.cpp
+++ b/src/plugins/qmljsinspector/qmljsdelta.cpp
@@ -246,8 +246,11 @@ static QString _methodName(UiSourceElement *source)
 
 
 
-Delta::DebugIdMap Delta::operator()(Document::Ptr doc1, Document::Ptr doc2, const DebugIdMap &debugIds)
+Delta::DebugIdMap Delta::operator()(const Document::Ptr &doc1, const Document::Ptr &doc2, const DebugIdMap &debugIds)
 {
+    Q_ASSERT(doc1->qmlProgram());
+    Q_ASSERT(doc2->qmlProgram());
+
     QHash< UiObjectMember*, QList<QDeclarativeDebugObjectReference > > newDebuggIds;
 
     Map M = Mapping(doc1, doc2);
diff --git a/src/plugins/qmljsinspector/qmljsdelta.h b/src/plugins/qmljsinspector/qmljsdelta.h
index 30f06fce93c..38d99223783 100644
--- a/src/plugins/qmljsinspector/qmljsdelta.h
+++ b/src/plugins/qmljsinspector/qmljsdelta.h
@@ -56,7 +56,7 @@ public:
 
 public:
     typedef QHash< UiObjectMember*, QList<QDeclarativeDebugObjectReference > > DebugIdMap;
-    DebugIdMap operator()(Document::Ptr doc1, Document::Ptr doc2, const DebugIdMap& debugIds);
+    DebugIdMap operator()(const QmlJS::Document::Ptr &doc1, const QmlJS::Document::Ptr &doc2, const DebugIdMap &debugIds);
 
     QList<Change> changes() const;
 
diff --git a/src/plugins/qmljsinspector/qmljslivetextpreview.cpp b/src/plugins/qmljsinspector/qmljslivetextpreview.cpp
index b43bdf69467..2adcc39e7ba 100644
--- a/src/plugins/qmljsinspector/qmljslivetextpreview.cpp
+++ b/src/plugins/qmljsinspector/qmljslivetextpreview.cpp
@@ -140,7 +140,7 @@ void QmlJSLiveTextPreview::documentChanged(QmlJS::Document::Ptr doc)
     if (!core->hasContext(dbgcontext))
         return;
 
-    if (doc && m_previousDoc && doc->fileName() == m_previousDoc->fileName()) {
+    if (doc && m_previousDoc && doc->fileName() == m_previousDoc->fileName() && doc->qmlProgram() && m_previousDoc->qmlProgram()) {
         if (m_debugIds.isEmpty())
             m_debugIds = m_initialTable.value(doc->fileName());
         Delta delta;