diff --git a/src/ConverterCache.cpp b/src/ConverterCache.cpp
index 14dce2d539..96efb0ffb0 100644
--- a/src/ConverterCache.cpp
+++ b/src/ConverterCache.cpp
@@ -249,21 +249,6 @@ void ConverterCache::init()
 }
 
 
-static bool changeMode(FileName const & fname, unsigned long int mode)
-{
-	if (mode == (unsigned long int)-1)
-		return true;
-
-	ofstream ofs(fname.toFilesystemEncoding().c_str(), ios::binary | ios::out | ios::trunc);
-	if (!ofs)
-		return false;
-	ofs.close();
-	if (!chmod(fname, mode))
-		return false;
-	return true;
-}
-
-
 void ConverterCache::add(FileName const & orig_from, string const & to_format,
 		FileName const & converted_file) const
 {
@@ -307,7 +292,7 @@ void ConverterCache::add(FileName const & orig_from, string const & to_format,
 		              onlyFilename(item->cache_name.absFilename()))) {
 			LYXERR(Debug::FILES, "Could not copy file " << orig_from << " to "
 				<< item->cache_name);
-		} else if (!changeMode(item->cache_name, 0600)) {
+		} else if (!item->cache_name.changeMode(0600)) {
 			LYXERR(Debug::FILES, "Could not change file mode"
 				<< item->cache_name);
 		}
@@ -316,7 +301,7 @@ void ConverterCache::add(FileName const & orig_from, string const & to_format,
 				orig_from.checksum());
 		if (mover.copy(converted_file, new_item.cache_name,
 		              onlyFilename(new_item.cache_name.absFilename()))) {
-			if (!changeMode(new_item.cache_name, 0600)) {
+			if (!new_item.cache_name.changeMode(0600)) {
 				LYXERR(Debug::FILES, "Could not change file mode"
 					<< new_item.cache_name);
 			}
diff --git a/src/support/FileName.cpp b/src/support/FileName.cpp
index 92d411820c..63f13e2325 100644
--- a/src/support/FileName.cpp
+++ b/src/support/FileName.cpp
@@ -60,7 +60,9 @@ struct FileName::Private
 	Private() {}
 
 	Private(string const & abs_filename) : fi(toqstr(abs_filename))
-	{}
+	{
+		fi.setCaching(fi.exists() ? true : false);
+	}
 	///
 	QFileInfo fi;
 };
@@ -148,6 +150,21 @@ bool FileName::renameTo(FileName const & name) const
 }
 
 
+bool FileName::changePermission(unsigned long int mode) const
+{
+	if (!fname.isWritable()) {
+		LYXERR0("File " << *this << " is not writable!");
+		return false;
+	}
+
+	if (!chmod(fname, mode)) {
+		LYXERR0("File " << *this << " cannot be changed to " << mode << " mode!");
+		return false;
+	}
+	return true;
+}
+
+
 string FileName::toFilesystemEncoding() const
 {
 	QByteArray const encoded = QFile::encodeName(d->fi.absoluteFilePath());
diff --git a/src/support/FileName.h b/src/support/FileName.h
index 328602bf34..b74ca1bf17 100644
--- a/src/support/FileName.h
+++ b/src/support/FileName.h
@@ -102,6 +102,9 @@ public:
 	/// \retrun true on success.
 	bool renameTo(FileName const & target) const;
 
+	/// change mode of pointed file.
+	/// \retrun true on success.
+	bool changeMode(unsigned long int mode) const;
 
 	/// remove directory and all contents, returns true on success
 	bool destroyDirectory() const;