diff --git a/generator/codegenerator.cpp b/generator/codegenerator.cpp
index c4a9563..b532f5d 100644
--- a/generator/codegenerator.cpp
+++ b/generator/codegenerator.cpp
@@ -29,7 +29,7 @@ void CodeGenerator::addDeclaration(clang::Decl *decl)
 void CodeGenerator::lazyInitializeSourceManager() const
 {
     if (factory().compilerInstance()) {
-        const_cast<CodeGenerator *>(this)->m_sourceManager = &factory().compilerInstance()->getSourceManager();
+        m_sourceManager = &factory().compilerInstance()->getSourceManager();
     }
 }
 
diff --git a/generator/codegenerator.h b/generator/codegenerator.h
index c8c3490..0c5de9d 100644
--- a/generator/codegenerator.h
+++ b/generator/codegenerator.h
@@ -36,7 +36,7 @@ protected:
 
 private:
     CodeFactory &m_factory;
-    const clang::SourceManager *m_sourceManager;
+    mutable const clang::SourceManager *m_sourceManager;
 };
 
 inline CodeGenerator::CodeGenerator(CodeFactory &factory)