diff --git a/src/support/unicode.cpp b/src/support/unicode.cpp
index 954aa79322..26f834a58b 100644
--- a/src/support/unicode.cpp
+++ b/src/support/unicode.cpp
@@ -52,8 +52,12 @@ namespace lyx {
 static const iconv_t invalid_cd = (iconv_t)(-1);
 
 
-struct IconvProcessor::Impl
+class IconvProcessor::Impl
 {
+	// noncopyable because iconv_close() is called in destructor
+	Impl(Impl const &);
+	Impl & operator=(Impl const &);
+public:
 	Impl(string const & to, string const & from)
 		: cd(invalid_cd), tocode_(to), fromcode_(from)
 	{}
diff --git a/src/support/unicode.h b/src/support/unicode.h
index 87a8392158..aad4f8d408 100644
--- a/src/support/unicode.h
+++ b/src/support/unicode.h
@@ -68,7 +68,7 @@ private:
 	/// \return true if the processor is ready to use.
 	bool init();
 	/// hide internals
-	struct Impl;
+	class Impl;
 	Impl * pimpl_;
 };