diff --git a/debug.js b/debug.js
new file mode 100644
index 000000000..b7939c251
--- /dev/null
+++ b/debug.js
@@ -0,0 +1 @@
+module.exports = require("./src/index-debug");
\ No newline at end of file
diff --git a/src/index-debug.js b/src/index-debug.js
new file mode 100644
index 000000000..0ea1166a2
--- /dev/null
+++ b/src/index-debug.js
@@ -0,0 +1,53 @@
+// WARNING: highly experimental.
+// might eventually become a starting point for a real debug build.
+
+"use strict";
+var protobuf = module.exports = require(".");
+
+// Count number of calls to any generated function
+protobuf.util.codegen = (function(codegen) { return function codegen_debug() {
+    codegen_debug.supported = codegen.supported;
+    codegen_debug.verbose = codegen.verbose;
+    var gen = codegen.apply(null, Array.prototype.slice.call(arguments));
+    gen.str = (function(str) { return function str_debug() {
+        return str.apply(null, Array.prototype.slice.call(arguments)).replace(/function ([^(]+)\(([^)]*)\) {/g, "function $1($2) {\n\t$1.calls=($1.calls|0)+1");
+    };})(gen.str);
+    return gen;
+};})(protobuf.util.codegen);
+
+/**
+ * Debugging utility functions. Only present in debug builds.
+ * @namespace
+ */
+var debug = protobuf.debug = {};
+
+/**
+ * Returns a list of unused types within the specified root.
+ * @param {NamespaceBase} ns Namespace to search
+ * @returns {Type[]} Unused types
+ */
+debug.unusedTypes = function unusedTypes(ns) {
+
+    /* istanbul ignore next */
+    if (!(ns instanceof protobuf.Namespace))
+        throw TypeError("ns must be a namespace");
+    /* istanbul ignore next */
+    if (!ns.nested)
+        return [];
+
+    var unused = [];
+    Object.keys(ns.nested).forEach(function(name) {
+        var nested = ns.nested[name];
+        if (nested instanceof protobuf.Type) {
+            var calls = (nested.encode.calls|0)
+                      + (nested.decode.calls|0)
+                      + (nested.verify.calls|0)
+                      + (nested.toObject.calls|0)
+                      + (nested.fromObject.calls|0);
+            if (!calls)
+                unused.push(nested);
+        } else if (nested instanceof protobuf.Namespace)
+            Array.prototype.push.apply(unused, unusedTypes(nested));
+    });
+    return unused;
+};
diff --git a/tests/other_basics.js b/tests/other_basics-debug.js
similarity index 81%
rename from tests/other_basics.js
rename to tests/other_basics-debug.js
index bdce35949..2225f55b4 100644
--- a/tests/other_basics.js
+++ b/tests/other_basics-debug.js
@@ -1,6 +1,6 @@
 var tape = require("tape");
 
-var protobuf = require("..");
+var protobuf = require("../debug");
 
 tape.test("google.protobuf.Any type", function(test) {
     protobuf.load("tests/data/common.proto", function(err, root) {
@@ -82,6 +82,20 @@ tape.test("google.protobuf.Any type", function(test) {
                 test.end();
             });
 
+            test.test(test.name + " - debug", function(test) {
+                var unused = protobuf.debug.unusedTypes(root).map(function(type) { return type.fullName; });
+                test.same(unused, [
+                    ".Something",
+                    ".google.protobuf.Duration",
+                    ".google.protobuf.Empty",
+                    ".google.protobuf.Struct",
+                    ".google.protobuf.Value",
+                    ".google.protobuf.ListValue",
+                    ".google.protobuf.Timestamp"
+                ], "should recognize unused types (all but .google.protobuf.Any)");
+                test.end();
+            });
+
             test.end();
         });