diff --git a/taglib/asf/asffile.cpp b/taglib/asf/asffile.cpp
index acfbe759..5c23ceb3 100644
--- a/taglib/asf/asffile.cpp
+++ b/taglib/asf/asffile.cpp
@@ -148,7 +148,11 @@ public:
 
 void ASF::File::BaseObject::parse(ASF::File *file, unsigned int size)
 {
-  data = file->readBlock(size - 24);
+  data.clear();
+  if (size > 24 && size <= file->length())
+    data = file->readBlock(size - 24);
+  else
+    data = ByteVector::null;
 }
 
 ByteVector ASF::File::BaseObject::render(ASF::File * /*file*/)
diff --git a/taglib/fileref.h b/taglib/fileref.h
index 46da1430..0f0c21a4 100644
--- a/taglib/fileref.h
+++ b/taglib/fileref.h
@@ -149,6 +149,9 @@ namespace TagLib {
      * \warning This pointer will become invalid when this FileRef and all
      * copies pass out of scope.
      *
+     * \warning Do not cast it to any subclasses of \class Tag.
+     * Use tag returning methods of appropriate subclasses of \class File instead.
+     *
      * \see File::tag()
      */
     Tag *tag() const;
diff --git a/taglib/toolkit/tstring.h b/taglib/toolkit/tstring.h
index a45c446e..693d043f 100644
--- a/taglib/toolkit/tstring.h
+++ b/taglib/toolkit/tstring.h
@@ -37,6 +37,9 @@
  * \relates TagLib::String
  *
  * Converts a QString to a TagLib::String without a requirement to link to Qt.
+ *
+ * \note consider conversion via usual char-by-char for loop to avoid UTF16->UTF8->UTF16
+ * conversion happening in the background
  */
 #define QStringToTString(s) TagLib::String(s.utf8().data(), TagLib::String::UTF8)
 
@@ -44,6 +47,10 @@
  * \relates TagLib::String
  *
  * Converts a TagLib::String to a QString without a requirement to link to Qt.
+ *
+ * \note consider conversion via usual char-by-char for loop to avoid UTF16->UTF8->UTF16
+ * conversion happening in the background
+ *
  */
 #define TStringToQString(s) QString::fromUtf8(s.toCString(true))