diff --git a/taglib/ape/apetag.cpp b/taglib/ape/apetag.cpp
index c633d575..00e1bc77 100644
--- a/taglib/ape/apetag.cpp
+++ b/taglib/ape/apetag.cpp
@@ -195,7 +195,7 @@ PropertyMap APE::Tag::properties() const
     String tagName = it->first.upper();
     // if the item is Binary or Locator, or if the key is an invalid string,
     // add to unsupportedData
-    if(it->second.type() != Item::Text || tagName.isNull())
+    if(it->second.type() != Item::Text || tagName.isEmpty())
       properties.unsupportedData().append(it->first);
     else {
       // Some tags need to be handled specially
@@ -232,7 +232,7 @@ PropertyMap APE::Tag::setProperties(const PropertyMap &origProps)
   for(; remIt != itemListMap().end(); ++remIt) {
     String key = remIt->first.upper();
     // only remove if a) key is valid, b) type is text, c) key not contained in new properties
-    if(!key.isNull() && remIt->second.type() == APE::Item::Text && !properties.contains(key))
+    if(!key.isEmpty() && remIt->second.type() == APE::Item::Text && !properties.contains(key))
       toRemove.append(remIt->first);
   }
 
diff --git a/taglib/mod/modtag.cpp b/taglib/mod/modtag.cpp
index 4ba72117..4b180bbb 100644
--- a/taglib/mod/modtag.cpp
+++ b/taglib/mod/modtag.cpp
@@ -128,7 +128,7 @@ PropertyMap Mod::Tag::properties() const
   PropertyMap properties;
   properties["TITLE"] = d->title;
   properties["COMMENT"] = d->comment;
-  if(!(d->trackerName.isNull()))
+  if(!(d->trackerName.isEmpty()))
     properties["TRACKERNAME"] = d->trackerName;
   return properties;
 }
diff --git a/taglib/mpeg/id3v2/frames/commentsframe.cpp b/taglib/mpeg/id3v2/frames/commentsframe.cpp
index deaa9d9a..b5618322 100644
--- a/taglib/mpeg/id3v2/frames/commentsframe.cpp
+++ b/taglib/mpeg/id3v2/frames/commentsframe.cpp
@@ -116,8 +116,6 @@ PropertyMap CommentsFrame::asProperties() const
   PropertyMap map;
   if(key.isEmpty() || key == "COMMENT")
     map.insert("COMMENT", text());
-  else if(key.isNull())
-    map.unsupportedData().append(L"COMM/" + description());
   else
     map.insert("COMMENT:" + key, text());
   return map;
@@ -164,7 +162,7 @@ void CommentsFrame::parseFields(const ByteVector &data)
     } else {
       d->description = String(l.front(), d->textEncoding);
       d->text = String(l.back(), d->textEncoding);
-    }  
+    }
   }
 }
 
diff --git a/taglib/mpeg/id3v2/frames/synchronizedlyricsframe.cpp b/taglib/mpeg/id3v2/frames/synchronizedlyricsframe.cpp
index 86c11f7a..2ab46481 100644
--- a/taglib/mpeg/id3v2/frames/synchronizedlyricsframe.cpp
+++ b/taglib/mpeg/id3v2/frames/synchronizedlyricsframe.cpp
@@ -159,7 +159,7 @@ void SynchronizedLyricsFrame::parseFields(const ByteVector &data)
   int pos = 6;
 
   d->description = readStringField(data, d->textEncoding, &pos);
-  if(d->description.isNull())
+  if(d->description.isEmpty())
     return;
 
   /*
@@ -190,7 +190,7 @@ void SynchronizedLyricsFrame::parseFields(const ByteVector &data)
       }
     }
     String text = readStringField(data, enc, &pos);
-    if(text.isNull() || pos + 4 > end)
+    if(text.isEmpty() || pos + 4 > end)
       return;
 
     uint time = data.toUInt(pos, true);
diff --git a/taglib/mpeg/id3v2/frames/textidentificationframe.cpp b/taglib/mpeg/id3v2/frames/textidentificationframe.cpp
index 07bf0ede..7eacf932 100644
--- a/taglib/mpeg/id3v2/frames/textidentificationframe.cpp
+++ b/taglib/mpeg/id3v2/frames/textidentificationframe.cpp
@@ -292,7 +292,7 @@ PropertyMap TextIdentificationFrame::makeTMCLProperties() const
   StringList l = fieldList();
   for(StringList::ConstIterator it = l.begin(); it != l.end(); ++it) {
     String instrument = it->upper();
-    if(instrument.isNull()) {
+    if(instrument.isEmpty()) {
       // instrument is not a valid key -> frame unsupported
       map.clear();
       map.unsupportedData().append(frameID());
diff --git a/taglib/mpeg/id3v2/frames/unsynchronizedlyricsframe.cpp b/taglib/mpeg/id3v2/frames/unsynchronizedlyricsframe.cpp
index 8f96cb8d..f97cdc5a 100644
--- a/taglib/mpeg/id3v2/frames/unsynchronizedlyricsframe.cpp
+++ b/taglib/mpeg/id3v2/frames/unsynchronizedlyricsframe.cpp
@@ -119,8 +119,6 @@ PropertyMap UnsynchronizedLyricsFrame::asProperties() const
   String key = description().upper();
   if(key.isEmpty() || key.upper() == "LYRICS")
     map.insert("LYRICS", text());
-  else if(key.isNull())
-    map.unsupportedData().append(L"USLT/" + description());
   else
     map.insert("LYRICS:" + key, text());
   return map;
@@ -164,7 +162,7 @@ void UnsynchronizedLyricsFrame::parseFields(const ByteVector &data)
     } else {
       d->description = String(l.front(), d->textEncoding);
       d->text = String(l.back(), d->textEncoding);
-    }  
+    }
   }
 }
 
diff --git a/taglib/mpeg/id3v2/frames/urllinkframe.cpp b/taglib/mpeg/id3v2/frames/urllinkframe.cpp
index e42d64d1..e59a80dd 100644
--- a/taglib/mpeg/id3v2/frames/urllinkframe.cpp
+++ b/taglib/mpeg/id3v2/frames/urllinkframe.cpp
@@ -159,8 +159,6 @@ PropertyMap UserUrlLinkFrame::asProperties() const
   String key = description().upper();
   if(key.isEmpty() || key.upper() == "URL")
     map.insert("URL", url());
-  else if(key.isNull())
-    map.unsupportedData().append(L"WXXX/" + description());
   else
     map.insert("URL:" + key, url());
   return map;
diff --git a/taglib/tag.cpp b/taglib/tag.cpp
index eb8fab7a..d13b248f 100644
--- a/taglib/tag.cpp
+++ b/taglib/tag.cpp
@@ -58,15 +58,15 @@ bool Tag::isEmpty() const
 PropertyMap Tag::properties() const
 {
   PropertyMap map;
-  if(!(title().isNull()))
+  if(!(title().isEmpty()))
     map["TITLE"].append(title());
-  if(!(artist().isNull()))
+  if(!(artist().isEmpty()))
     map["ARTIST"].append(artist());
-  if(!(album().isNull()))
+  if(!(album().isEmpty()))
     map["ALBUM"].append(album());
-  if(!(comment().isNull()))
+  if(!(comment().isEmpty()))
     map["COMMENT"].append(comment());
-  if(!(genre().isNull()))
+  if(!(genre().isEmpty()))
     map["GENRE"].append(genre());
   if(!(year() == 0))
     map["DATE"].append(String::number(year()));
diff --git a/taglib/toolkit/tpropertymap.cpp b/taglib/toolkit/tpropertymap.cpp
index 313d7fb4..2c696417 100644
--- a/taglib/toolkit/tpropertymap.cpp
+++ b/taglib/toolkit/tpropertymap.cpp
@@ -35,7 +35,7 @@ PropertyMap::PropertyMap(const SimplePropertyMap &m)
 {
   for(SimplePropertyMap::ConstIterator it = m.begin(); it != m.end(); ++it){
     String key = it->first.upper();
-    if(!key.isNull())
+    if(!key.isEmpty())
       insert(it->first, it->second);
     else
       unsupported.append(it->first);