diff --git a/core/generator.cpp b/core/generator.cpp
index 30fcd6a4a..5d4a95561 100644
--- a/core/generator.cpp
+++ b/core/generator.cpp
@@ -284,7 +284,7 @@ void Generator::signalPixmapRequestDone( PixmapRequest * request )
         Q_ASSERT( !"No document set for generator in signalPixmapRequestDone!" );
 }
 
-Document * Generator::document() const
+const Document * Generator::document() const
 {
     return d->m_document;
 }
diff --git a/core/generator.h b/core/generator.h
index 7905ad26b..46464f606 100644
--- a/core/generator.h
+++ b/core/generator.h
@@ -390,7 +390,7 @@ class OKULAR_EXPORT Generator : public QObject
         /**
          * Returns a pointer to the document.
          */
-        Document * document() const;
+        const Document * document() const;
 
         /**
          * Toggle the @p feature .