diff --git a/XPath/impl/xpath_function_resolver.hpp b/XPath/impl/xpath_function_resolver.hpp
index 3b5717b5..234e8f0f 100644
--- a/XPath/impl/xpath_function_resolver.hpp
+++ b/XPath/impl/xpath_function_resolver.hpp
@@ -25,7 +25,11 @@ public:
                                          const std::vector<XPathExpressionPtr>& argExprs) const = 0; 
 }; // class FunctionResolver
 
-typedef boost::shared_ptr<FunctionResolver> FunctionResolverPtr;
+class FunctionResolverPtr : public boost::shared_ptr<FunctionResolver> 
+{
+public:
+  explicit FunctionResolverPtr(FunctionResolver* fr) : boost::shared_ptr<FunctionResolver>(fr) { }
+}; 
 
 class NullFunctionResolver : public FunctionResolver
 {
diff --git a/XPath/impl/xpath_namespace_context.hpp b/XPath/impl/xpath_namespace_context.hpp
index 25b43aa7..2fbcf18c 100644
--- a/XPath/impl/xpath_namespace_context.hpp
+++ b/XPath/impl/xpath_namespace_context.hpp
@@ -33,7 +33,11 @@ class NamespaceContext
     bool operator==(const NamespaceContext&) const;
 }; // class NamespaceContext 
 
-typedef boost::shared_ptr<NamespaceContext> NamespaceContextPtr;
+class NamespaceContextPtr : public boost::shared_ptr<NamespaceContext> 
+{
+public:
+  explicit NamespaceContextPtr(NamespaceContext* nc) : boost::shared_ptr<NamespaceContext>(nc) { }
+}; // class NamespaceContextPtr
 
 class NullNamespaceContext : public NamespaceContext
 {  
diff --git a/XPath/impl/xpath_variable_resolver.hpp b/XPath/impl/xpath_variable_resolver.hpp
index fc17d5b2..91d8ce91 100644
--- a/XPath/impl/xpath_variable_resolver.hpp
+++ b/XPath/impl/xpath_variable_resolver.hpp
@@ -23,7 +23,11 @@ public:
   virtual XPathValuePtr resolveVariable(const std::string& name) const = 0; 
 }; // class VariableResolver
 
-typedef boost::shared_ptr<VariableResolver> VariableResolverPtr;
+class VariableResolverPtr : public boost::shared_ptr<VariableResolver>
+{
+public:
+  explicit VariableResolverPtr(VariableResolver* vr) : boost::shared_ptr<VariableResolver>(vr) { }
+}; // class VariableResolverPtr
 
 class NullVariableResolver : public VariableResolver
 {