--- src/lib/WPXPropertyList.cpp	2012-09-24 11:55:06.000000000 +0200
+++ src/lib/WPXPropertyList.cpp	2012-09-24 14:25:10.401619900 +0200
@@ -171,7 +171,7 @@
 	m_mapImpl->remove(name);
 }
 
-WPXPropertyList &WPXPropertyList::operator=(const WPXPropertyList &propList)
+const WPXPropertyList &WPXPropertyList::operator=(const WPXPropertyList &propList)
 {
 	WPXPropertyList tmp(propList);
 	std::swap(m_mapImpl, tmp.m_mapImpl);
--- src/lib/WPXPropertyList.h	2012-09-24 13:48:08.667113100 +0200
+++ src/lib/WPXPropertyList.h	2012-09-24 14:25:10.401619900 +0200
@@ -50,7 +50,7 @@
 
 	void remove(const char *name);
 	const WPXProperty *operator[](const char *name) const;
-	WPXPropertyList &operator=(const WPXPropertyList &propList);
+	const WPXPropertyList &operator=(const WPXPropertyList &propList);
 	void clear();
 
 	class Iter