diff --git a/messageviewer/autotests/setupenv.h b/messageviewer/autotests/setupenv.h
--- a/messageviewer/autotests/setupenv.h
+++ b/messageviewer/autotests/setupenv.h
@@ -58,35 +58,35 @@
         return mCSSHelper;
     }
 
-    bool htmlLoadExternal() Q_DECL_OVERRIDE {
+    bool htmlLoadExternal() const Q_DECL_OVERRIDE {
         return mHtmlLoadExternal;
     }
 
     void setHtmlLoadExternal(bool loadExternal)
     {
         mHtmlLoadExternal = loadExternal;
     }
 
-    bool htmlMail() Q_DECL_OVERRIDE {
+    bool htmlMail() const Q_DECL_OVERRIDE {
         return mHtmlMail;
     }
 
     void setHtmlMail(bool htmlMail)
     {
         mHtmlMail = htmlMail;
     }
 
-    bool autoImportKeys() Q_DECL_OVERRIDE
+    bool autoImportKeys() const Q_DECL_OVERRIDE
     {
         return true;
     }
 
-    bool showEmoticons() Q_DECL_OVERRIDE
+    bool showEmoticons() const Q_DECL_OVERRIDE
     {
         return false;
     }
 
-    bool showExpandQuotesMark() Q_DECL_OVERRIDE
+    bool showExpandQuotesMark() const Q_DECL_OVERRIDE
     {
         return false;
     }
diff --git a/messageviewer/src/objecttreesourceif.h b/messageviewer/src/objecttreesourceif.h
--- a/messageviewer/src/objecttreesourceif.h
+++ b/messageviewer/src/objecttreesourceif.h
@@ -58,19 +58,19 @@
     virtual void setHtmlMode(MessageViewer::Util::HtmlMode mode) = 0;
 
     /** Return true if the mail should be parsed as a html mail */
-    virtual bool htmlMail() = 0;
+    virtual bool htmlMail() const = 0;
 
     /** Return true if an encrypted mail should be decrypted */
 
-    virtual bool decryptMessage() = 0;
+    virtual bool decryptMessage() const = 0;
 
     /** Return true if external sources should be loaded in a html mail */
-    virtual bool htmlLoadExternal() = 0;
+    virtual bool htmlLoadExternal() const = 0;
 
     /** Return true to include the signature details in the generated html */
-    virtual bool showSignatureDetails() = 0;
+    virtual bool showSignatureDetails() const = 0;
 
-    virtual int levelQuote() = 0;
+    virtual int levelQuote() const = 0;
 
     /** The override codec that should be used for the mail */
     virtual const QTextCodec *overrideCodec() = 0;
@@ -90,11 +90,11 @@
     virtual QObject *sourceObject() = 0;
 
     /** should keys be imported automatically **/
-    virtual bool autoImportKeys() = 0;
+    virtual bool autoImportKeys() const = 0;
 
-    virtual bool showEmoticons() = 0;
+    virtual bool showEmoticons() const = 0;
 
-    virtual bool showExpandQuotesMark() = 0;
+    virtual bool showExpandQuotesMark() const = 0;
 };
 }
 
diff --git a/messageviewer/src/viewer/objecttreeemptysource.h b/messageviewer/src/viewer/objecttreeemptysource.h
--- a/messageviewer/src/viewer/objecttreeemptysource.h
+++ b/messageviewer/src/viewer/objecttreeemptysource.h
@@ -34,23 +34,23 @@
 public:
     EmptySource();
     ~EmptySource();
-    bool htmlMail() Q_DECL_OVERRIDE;
-    bool decryptMessage() Q_DECL_OVERRIDE;
-    bool htmlLoadExternal() Q_DECL_OVERRIDE;
-    bool showSignatureDetails() Q_DECL_OVERRIDE;
+    bool htmlMail() const Q_DECL_OVERRIDE;
+    bool decryptMessage() const Q_DECL_OVERRIDE;
+    bool htmlLoadExternal() const Q_DECL_OVERRIDE;
+    bool showSignatureDetails() const Q_DECL_OVERRIDE;
     void setHtmlMode(MessageViewer::Util::HtmlMode mode) Q_DECL_OVERRIDE;
     void setAllowDecryption(bool allowDecryption);
-    int levelQuote() Q_DECL_OVERRIDE;
+    int levelQuote() const Q_DECL_OVERRIDE;
     const QTextCodec *overrideCodec() Q_DECL_OVERRIDE;
     QString createMessageHeader(KMime::Message *message) Q_DECL_OVERRIDE;
     const AttachmentStrategy *attachmentStrategy() Q_DECL_OVERRIDE;
     HtmlWriter *htmlWriter() Q_DECL_OVERRIDE;
     CSSHelperBase *cssHelper() Q_DECL_OVERRIDE;
     QObject *sourceObject() Q_DECL_OVERRIDE;
 
-    bool autoImportKeys() Q_DECL_OVERRIDE;
-    bool showEmoticons() Q_DECL_OVERRIDE;
-    bool showExpandQuotesMark() Q_DECL_OVERRIDE;
+    bool autoImportKeys() const Q_DECL_OVERRIDE;
+    bool showEmoticons() const Q_DECL_OVERRIDE;
+    bool showExpandQuotesMark() const Q_DECL_OVERRIDE;
 private:
     EmptySourcePrivate *const d;
 };
diff --git a/messageviewer/src/viewer/objecttreeemptysource.cpp b/messageviewer/src/viewer/objecttreeemptysource.cpp
--- a/messageviewer/src/viewer/objecttreeemptysource.cpp
+++ b/messageviewer/src/viewer/objecttreeemptysource.cpp
@@ -47,22 +47,22 @@
     delete d;
 }
 
-bool EmptySource::htmlMail()
+bool EmptySource::htmlMail() const
 {
     return true;
 }
 
-bool EmptySource::decryptMessage()
+bool EmptySource::decryptMessage() const
 {
     return d->mAllowDecryption;
 }
 
-bool EmptySource::htmlLoadExternal()
+bool EmptySource::htmlLoadExternal() const
 {
     return false;
 }
 
-bool EmptySource::showSignatureDetails()
+bool EmptySource::showSignatureDetails() const
 {
     return false;
 }
@@ -77,7 +77,7 @@
     d->mAllowDecryption = allowDecryption;
 }
 
-int EmptySource::levelQuote()
+int EmptySource::levelQuote() const
 {
     return 1;
 }
@@ -113,17 +113,17 @@
     return 0;
 }
 
-bool EmptySource::autoImportKeys()
+bool EmptySource::autoImportKeys() const
 {
     return true;
 }
 
-bool EmptySource::showEmoticons()
+bool EmptySource::showEmoticons() const
 {
     return false;
 }
 
-bool EmptySource::showExpandQuotesMark()
+bool EmptySource::showExpandQuotesMark() const
 {
     return false;
 }
diff --git a/messageviewer/src/viewer/objecttreeviewersource.h b/messageviewer/src/viewer/objecttreeviewersource.h
--- a/messageviewer/src/viewer/objecttreeviewersource.h
+++ b/messageviewer/src/viewer/objecttreeviewersource.h
@@ -35,22 +35,22 @@
 public:
     explicit MailViewerSource(ViewerPrivate *viewer);
     ~MailViewerSource();
-    bool htmlMail() Q_DECL_OVERRIDE;
-    bool decryptMessage() Q_DECL_OVERRIDE;
-    bool htmlLoadExternal() Q_DECL_OVERRIDE;
-    bool showSignatureDetails() Q_DECL_OVERRIDE;
+    bool htmlMail() const Q_DECL_OVERRIDE;
+    bool decryptMessage() const Q_DECL_OVERRIDE;
+    bool htmlLoadExternal() const Q_DECL_OVERRIDE;
+    bool showSignatureDetails() const Q_DECL_OVERRIDE;
     void setHtmlMode(Util::HtmlMode mode) Q_DECL_OVERRIDE;
-    int levelQuote() Q_DECL_OVERRIDE;
+    int levelQuote() const Q_DECL_OVERRIDE;
     const QTextCodec *overrideCodec() Q_DECL_OVERRIDE;
     QString createMessageHeader(KMime::Message *message) Q_DECL_OVERRIDE;
     const AttachmentStrategy *attachmentStrategy() Q_DECL_OVERRIDE;
     HtmlWriter *htmlWriter() Q_DECL_OVERRIDE;
     CSSHelperBase *cssHelper() Q_DECL_OVERRIDE;
     QObject *sourceObject() Q_DECL_OVERRIDE;
 
-    bool autoImportKeys() Q_DECL_OVERRIDE;
-    bool showEmoticons() Q_DECL_OVERRIDE;
-    bool showExpandQuotesMark() Q_DECL_OVERRIDE;
+    bool autoImportKeys() const Q_DECL_OVERRIDE;
+    bool showEmoticons() const Q_DECL_OVERRIDE;
+    bool showExpandQuotesMark() const Q_DECL_OVERRIDE;
 private:
     ViewerPrivate *mViewer;
 };
diff --git a/messageviewer/src/viewer/objecttreeviewersource.cpp b/messageviewer/src/viewer/objecttreeviewersource.cpp
--- a/messageviewer/src/viewer/objecttreeviewersource.cpp
+++ b/messageviewer/src/viewer/objecttreeviewersource.cpp
@@ -34,22 +34,22 @@
 {
 }
 
-bool MailViewerSource::htmlMail()
+bool MailViewerSource::htmlMail() const
 {
     return mViewer->htmlMail();
 }
 
-bool MailViewerSource::decryptMessage()
+bool MailViewerSource::decryptMessage() const
 {
     return mViewer->decryptMessage();
 }
 
-bool MailViewerSource::htmlLoadExternal()
+bool MailViewerSource::htmlLoadExternal() const
 {
     return mViewer->htmlLoadExternal();
 }
 
-bool MailViewerSource::showSignatureDetails()
+bool MailViewerSource::showSignatureDetails() const
 {
     return mViewer->mShowSignatureDetails;
 }
@@ -59,7 +59,7 @@
     mViewer->mColorBar->setMode(mode);
 }
 
-int MailViewerSource::levelQuote()
+int MailViewerSource::levelQuote() const
 {
     return mViewer->mLevelQuote;
 }
@@ -94,17 +94,17 @@
     return mViewer->cssHelper();
 }
 
-bool MailViewerSource::autoImportKeys()
+bool MailViewerSource::autoImportKeys() const
 {
     return MessageViewer::MessageViewerSettings::self()->autoImportKeys();
 }
 
-bool MailViewerSource::showEmoticons()
+bool MailViewerSource::showEmoticons() const
 {
     return MessageViewer::MessageViewerSettings::self()->showEmoticons();
 }
 
-bool MailViewerSource::showExpandQuotesMark()
+bool MailViewerSource::showExpandQuotesMark() const
 {
     return MessageViewer::MessageViewerSettings::self()->showExpandQuotesMark();
 }