diff --git a/taglib/ape/apefile.cpp b/taglib/ape/apefile.cpp
index b3da1379..491e24d7 100644
--- a/taglib/ape/apefile.cpp
+++ b/taglib/ape/apefile.cpp
@@ -112,15 +112,6 @@ TagLib::Tag *APE::File::tag() const
   return &d->tag;
 }
 
-PropertyMap APE::File::properties() const
-{
-  if(d->hasAPE)
-    return d->tag.access<APE::Tag>(ApeAPEIndex, false)->properties();
-  if(d->hasID3v1)
-    return d->tag.access<ID3v1::Tag>(ApeID3v1Index, false)->properties();
-  return PropertyMap();
-}
-
 void APE::File::removeUnsupportedProperties(const StringList &properties)
 {
   if(d->hasAPE)
diff --git a/taglib/ape/apefile.h b/taglib/ape/apefile.h
index cfee50da..cdd37062 100644
--- a/taglib/ape/apefile.h
+++ b/taglib/ape/apefile.h
@@ -113,13 +113,6 @@ namespace TagLib {
        */
       virtual TagLib::Tag *tag() const;
 
-      /*!
-       * Implements the unified property interface -- export function.
-       * If the file contains both an APE and an ID3v1 tag, only APE
-       * will be converted to the PropertyMap.
-       */
-      PropertyMap properties() const;
-
       /*!
        * Removes unsupported properties. Forwards to the actual Tag's
        * removeUnsupportedProperties() function.
diff --git a/taglib/flac/flacfile.cpp b/taglib/flac/flacfile.cpp
index e0faa18d..ef0325e5 100644
--- a/taglib/flac/flacfile.cpp
+++ b/taglib/flac/flacfile.cpp
@@ -138,19 +138,6 @@ TagLib::Tag *FLAC::File::tag() const
   return &d->tag;
 }
 
-PropertyMap FLAC::File::properties() const
-{
-  // once Tag::properties() is virtual, this case distinction could actually be done
-  // within TagUnion.
-  if(d->hasXiphComment)
-    return d->tag.access<Ogg::XiphComment>(FlacXiphIndex, false)->properties();
-  if(d->hasID3v2)
-    return d->tag.access<ID3v2::Tag>(FlacID3v2Index, false)->properties();
-  if(d->hasID3v1)
-    return d->tag.access<ID3v1::Tag>(FlacID3v1Index, false)->properties();
-  return PropertyMap();
-}
-
 void FLAC::File::removeUnsupportedProperties(const StringList &unsupported)
 {
   if(d->hasXiphComment)
diff --git a/taglib/flac/flacfile.h b/taglib/flac/flacfile.h
index cf91a21e..1cd01d49 100644
--- a/taglib/flac/flacfile.h
+++ b/taglib/flac/flacfile.h
@@ -110,14 +110,6 @@ namespace TagLib {
        */
       virtual TagLib::Tag *tag() const;
 
-      /*!
-       * Implements the unified property interface -- export function.
-       * If the file contains more than one tag (e.g. XiphComment and ID3v1),
-       * only the first one (in the order XiphComment, ID3v2, ID3v1) will be
-       * converted to the PropertyMap.
-       */
-      PropertyMap properties() const;
-
       void removeUnsupportedProperties(const StringList &);
 
       /*!
diff --git a/taglib/mp4/mp4file.cpp b/taglib/mp4/mp4file.cpp
index f41ee888..f6e15e65 100644
--- a/taglib/mp4/mp4file.cpp
+++ b/taglib/mp4/mp4file.cpp
@@ -91,21 +91,6 @@ MP4::File::tag() const
   return d->tag;
 }
 
-PropertyMap MP4::File::properties() const
-{
-  return d->tag->properties();
-}
-
-void MP4::File::removeUnsupportedProperties(const StringList &properties)
-{
-  d->tag->removeUnsupportedProperties(properties);
-}
-
-PropertyMap MP4::File::setProperties(const PropertyMap &properties)
-{
-  return d->tag->setProperties(properties);
-}
-
 MP4::Properties *
 MP4::File::audioProperties() const
 {
diff --git a/taglib/mp4/mp4file.h b/taglib/mp4/mp4file.h
index 17fd5a95..2ed3bea5 100644
--- a/taglib/mp4/mp4file.h
+++ b/taglib/mp4/mp4file.h
@@ -88,22 +88,6 @@ namespace TagLib {
        */
       Tag *tag() const;
 
-      /*!
-       * Implements the unified property interface -- export function.
-       */
-      PropertyMap properties() const;
-
-      /*!
-       * Removes unsupported properties. Forwards to the actual Tag's
-       * removeUnsupportedProperties() function.
-       */
-      void removeUnsupportedProperties(const StringList &properties);
-
-      /*!
-       * Implements the unified property interface -- import function.
-       */
-      PropertyMap setProperties(const PropertyMap &);
-
       /*!
        * Returns the MP4 audio properties for this file.
        */
diff --git a/taglib/mpc/mpcfile.cpp b/taglib/mpc/mpcfile.cpp
index b27fb8d2..2638df85 100644
--- a/taglib/mpc/mpcfile.cpp
+++ b/taglib/mpc/mpcfile.cpp
@@ -116,15 +116,6 @@ TagLib::Tag *MPC::File::tag() const
   return &d->tag;
 }
 
-PropertyMap MPC::File::properties() const
-{
-  if(d->hasAPE)
-    return d->tag.access<APE::Tag>(MPCAPEIndex, false)->properties();
-  if(d->hasID3v1)
-    return d->tag.access<ID3v1::Tag>(MPCID3v1Index, false)->properties();
-  return PropertyMap();
-}
-
 void MPC::File::removeUnsupportedProperties(const StringList &properties)
 {
   if(d->hasAPE)
diff --git a/taglib/mpc/mpcfile.h b/taglib/mpc/mpcfile.h
index 887aa46d..1f47996f 100644
--- a/taglib/mpc/mpcfile.h
+++ b/taglib/mpc/mpcfile.h
@@ -113,13 +113,6 @@ namespace TagLib {
        */
       virtual TagLib::Tag *tag() const;
 
-      /*!
-       * Implements the unified property interface -- export function.
-       * If the file contains both an APE and an ID3v1 tag, only the APE
-       * tag  will be converted to the PropertyMap.
-       */
-      PropertyMap properties() const;
-
       void removeUnsupportedProperties(const StringList &properties);
 
       /*!
diff --git a/taglib/mpeg/id3v2/id3v2tag.h b/taglib/mpeg/id3v2/id3v2tag.h
index 6841bc5c..c58d4d86 100644
--- a/taglib/mpeg/id3v2/id3v2tag.h
+++ b/taglib/mpeg/id3v2/id3v2tag.h
@@ -326,7 +326,7 @@ namespace TagLib {
        *  once, the description, separated by a "/".
        *
        */
-      PropertyMap properties() const;
+      virtual PropertyMap properties() const;
 
       /*!
        * Removes unsupported frames given by \a properties. The elements of
@@ -339,13 +339,13 @@ namespace TagLib {
        *  - "UNKNOWN/" + frameID, for frames that could not be parsed by TagLib.
        *    In that case, *all* unknown frames with the given ID will be removed.
        */
-      void removeUnsupportedProperties(const StringList &properties);
+      virtual void removeUnsupportedProperties(const StringList &properties);
 
       /*!
        * Implements the unified property interface -- import function.
        * See the comments in properties().
        */
-      PropertyMap setProperties(const PropertyMap &);
+      virtual PropertyMap setProperties(const PropertyMap &);
 
       /*!
        * Render the tag back to binary data, suitable to be written to disk.
diff --git a/taglib/mpeg/mpegfile.cpp b/taglib/mpeg/mpegfile.cpp
index 1091ea14..5d1ac1fb 100644
--- a/taglib/mpeg/mpegfile.cpp
+++ b/taglib/mpeg/mpegfile.cpp
@@ -134,19 +134,6 @@ TagLib::Tag *MPEG::File::tag() const
   return &d->tag;
 }
 
-PropertyMap MPEG::File::properties() const
-{
-  // once Tag::properties() is virtual, this case distinction could actually be done
-  // within TagUnion.
-  if(d->hasID3v2)
-    return d->tag.access<ID3v2::Tag>(ID3v2Index, false)->properties();
-  if(d->hasAPE)
-    return d->tag.access<APE::Tag>(APEIndex, false)->properties();
-  if(d->hasID3v1)
-    return d->tag.access<ID3v1::Tag>(ID3v1Index, false)->properties();
-  return PropertyMap();
-}
-
 void MPEG::File::removeUnsupportedProperties(const StringList &properties)
 {
   if(d->hasID3v2)
diff --git a/taglib/mpeg/mpegfile.h b/taglib/mpeg/mpegfile.h
index 725dc19d..068432ad 100644
--- a/taglib/mpeg/mpegfile.h
+++ b/taglib/mpeg/mpegfile.h
@@ -132,14 +132,6 @@ namespace TagLib {
        */
       virtual Tag *tag() const;
 
-      /*!
-       * Implements the reading part of the unified property interface.
-       * If the file contains more than one tag, only the
-       * first one (in the order ID3v2, APE, ID3v1) will be converted to the
-       * PropertyMap.
-       */
-      PropertyMap properties() const;
-
       void removeUnsupportedProperties(const StringList &properties);
 
       /*!
diff --git a/taglib/ogg/xiphcomment.h b/taglib/ogg/xiphcomment.h
index 7fbc151d..bf94b69c 100644
--- a/taglib/ogg/xiphcomment.h
+++ b/taglib/ogg/xiphcomment.h
@@ -148,7 +148,7 @@ namespace TagLib {
        * comment is nothing more than a map from tag names to list of values,
        * as is the dict interface).
        */
-      PropertyMap properties() const;
+      virtual PropertyMap properties() const;
 
       /*!
        * Implements the unified property interface -- import function.
@@ -157,7 +157,7 @@ namespace TagLib {
        * containing '=' or '~') in which case the according values will
        * be contained in the returned PropertyMap.
        */
-      PropertyMap setProperties(const PropertyMap&);
+      virtual PropertyMap setProperties(const PropertyMap&);
 
       /*!
        * Check if the given String is a valid Xiph comment key.
diff --git a/taglib/tag.h b/taglib/tag.h
index 96612110..693b38b4 100644
--- a/taglib/tag.h
+++ b/taglib/tag.h
@@ -58,14 +58,14 @@ namespace TagLib {
      * The default implementation in this class considers only the usual built-in
      * tags (artist, album, ...) and only one value per key.
      */
-    PropertyMap properties() const;
+    virtual PropertyMap properties() const;
 
     /*!
      * Removes unsupported properties, or a subset of them, from the tag.
      * The parameter \a properties must contain only entries from
      * properties().unsupportedData().
      */
-    void removeUnsupportedProperties(const StringList& properties);
+    virtual void removeUnsupportedProperties(const StringList& properties);
 
     /*!
      * Sets the tags of this File to those specified in \a properties. This default
@@ -73,7 +73,7 @@ namespace TagLib {
      * (artist, album, ...), and only one value per key; the rest will be contained
      * in the returned PropertyMap.
      */
-    PropertyMap setProperties(const PropertyMap &properties);
+    virtual PropertyMap setProperties(const PropertyMap &properties);
 
     /*!
      * Returns the track name; if no track name is present in the tag
diff --git a/taglib/tagunion.cpp b/taglib/tagunion.cpp
index 52d7136b..4a5afd32 100644
--- a/taglib/tagunion.cpp
+++ b/taglib/tagunion.cpp
@@ -25,6 +25,7 @@
 
 #include "tagunion.h"
 #include "tstringlist.h"
+#include "tpropertymap.h"
 
 using namespace TagLib;
 
@@ -102,6 +103,16 @@ void TagUnion::set(int index, Tag *tag)
   d->tags[index] = tag;
 }
 
+PropertyMap TagUnion::properties() const
+{
+  for(uint i = 0; i < 3; ++i) {
+    if(tag(i)) {
+      return tag(i)->properties();
+    }
+  }
+  return PropertyMap();
+}
+
 String TagUnion::title() const
 {
   stringUnion(title);
diff --git a/taglib/tagunion.h b/taglib/tagunion.h
index e94d523a..98b4d338 100644
--- a/taglib/tagunion.h
+++ b/taglib/tagunion.h
@@ -56,6 +56,8 @@ namespace TagLib {
 
     void set(int index, Tag *tag);
 
+    virtual PropertyMap properties() const;
+    
     virtual String title() const;
     virtual String artist() const;
     virtual String album() const;