diff --git a/README.md b/README.md
index 96d7e08..9a46d3c 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@ Puget
 
 [![Build Status](https://travis-ci.org/greglook/puget.svg?branch=master)](https://travis-ci.org/greglook/puget)
 [![Coverage Status](https://coveralls.io/repos/greglook/puget/badge.png?branch=master)](https://coveralls.io/r/greglook/puget?branch=master)
-[![Dependency Status](https://www.versioneye.com/user/projects/53718bfb14c1589a89000144/badge.png)](https://www.versioneye.com/user/projects/53718bfb14c1589a89000144)
+[![Dependency Status](https://www.versioneye.com/user/projects/53718bfb14c1589a89000144/badge.png)](https://www.versioneye.com/clojure/mvxcvi:puget/0.5.1)
 
 Puget is a Clojure library for printing [EDN](https://github.com/edn-format/edn)
 values. Under the hood, Puget uses the
@@ -74,7 +74,7 @@ To use this version with Leiningen, add the following dependency to your project
 definition:
 
 ```clojure
-[mvxcvi/puget "0.5.0"]
+[mvxcvi/puget "0.5.1"]
 ```
 
 From the REPL, you can use the following helper functions for some control of
diff --git a/project.clj b/project.clj
index f531217..9510c37 100644
--- a/project.clj
+++ b/project.clj
@@ -1,4 +1,4 @@
-(defproject mvxcvi/puget "0.5.0"
+(defproject mvxcvi/puget "0.5.1"
   :description "Colorizing canonical Clojure printer for EDN values."
   :url "https://github.com/greglook/puget"
   :license {:name "Public Domain"
diff --git a/src/puget/data.clj b/src/puget/data.clj
index 65d9cf4..d7f4e35 100644
--- a/src/puget/data.clj
+++ b/src/puget/data.clj
@@ -121,18 +121,17 @@
 
 (defmacro extend-tagged-value
   "Extends the TaggedValue protocol with implementations which return the
-  given symbol as the tag and use the body to calculate the value. The symbol
-  'this' is bound to the data. This macro also defines a print-method which
+  given symbol as the tag and use the given expression to calculate the value.
+  The expression should resolve to a function which accepts one argument and
+  returns the serialized value. This macro also defines a print-method which
   delegates to edn-str."
   [t tag expr]
-  `(do
+  `(let [value-fn# ~expr]
      (extend-type ~t
        TaggedValue
-       (edn-tag [~'this] ~tag)
-       (edn-value [~'this]
-         ~(if (or (symbol? expr) (keyword? expr))
-            (list expr 'this)
-            expr)))
+       (edn-tag [this#] ~tag)
+       (edn-value [this#]
+         (value-fn# this#)))
      (defprint-method ~t)))
 
 
@@ -143,7 +142,8 @@
 
 (defmacro extend-tagged-map
   [c tag]
-  `(extend-tagged-value ~c ~tag (into {} (seq ~'this))))
+  `(extend-tagged-value ~c ~tag
+     (comp (partial into {}) seq)))
 
 
 
@@ -169,7 +169,7 @@
 ; #bin - Binary data in the form of byte arrays.
 (extend-tagged-value
   (class (byte-array 0)) 'bin
-  (->> this b64/encode (map char) (apply str)))
+  #(->> % b64/encode (map char) (apply str)))
 
 
 (defn read-bin