diff --git a/Gopkg.toml b/Gopkg.toml
index afdcaf360..2be00de46 100644
--- a/Gopkg.toml
+++ b/Gopkg.toml
@@ -88,6 +88,11 @@ ignored = [
   go-tests = true
   non-go = true
 
+  # To avoid deletion of jsbuiltin.inc.js
+  [[prune.project]]
+    name = "github.com/gopherjs/jsbuiltin"
+    non-go = false
+
 # Constraints / Overrides follow
 # Semantic versions (like v1.0.0) are preferred
 # Please keep alphabetized
diff --git a/vendor/github.com/gopherjs/jsbuiltin/README.md b/vendor/github.com/gopherjs/jsbuiltin/README.md
new file mode 100644
index 000000000..c107ae4f3
--- /dev/null
+++ b/vendor/github.com/gopherjs/jsbuiltin/README.md
@@ -0,0 +1,103 @@
+[![Build Status](https://api.travis-ci.org/gopherjs/jsbuiltin.svg?branch=master)](https://travis-ci.org/gopherjs/jsbuiltin) [![GoDoc](https://godoc.org/github.com/gopherjs/jsbuiltin?status.png)](http://godoc.org/github.com/gopherjs/jsbuiltin)
+
+jsbuiltin - Built-in JavaScript functions for GopherJS
+------------------------------------------------------
+
+JavaScript has a small number of [built-in
+functions](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects)
+to handle some common day-to-day tasks. This package providers wrappers around
+some of these functions for use in GopherJS.
+
+It is worth noting that in many cases, using Go's equivalent functionality
+(such as that found in the [net/url](https://golang.org/pkg/net/url/) package)
+may be preferable to using this package, and will be a necessity any time you
+wish to share functionality between front-end and back-end code.
+
+### What is supported?
+Not all JavaScript built-in functions make sense or are useful in a Go
+environment. The table below shows each of the JavaScript built-in functions,
+and its current state in this package.
+
+| Name                 | Supported | Comment                     |
+|----------------------|-----------|-----------------------------|
+| eval()               | --        |                             |
+| uneval()             | --        |                             |
+| isFinite()           | yes       |                             |
+| isNaN()              | yes       |                             |
+| parseFloat()         | TODO?     | See note below              |
+| parseInt()           | TODO?     | See note below              |
+| decodeURI()          | yes       |                             |
+| decodeURIComponent() | yes       |                             |
+| encodeURI()          | yes       |                             |
+| encodeURIComponent() | yes       |                             |
+| escape()             | --        | deprecated circa 2000       |
+| Number()             | --        | See note below              |
+| String()             | --        | Use js.Object.String()      |
+| unescape()           | --        | deprecated circa 2000       |
+| typeof operator      | yes       |                             |
+| instanceof operator  | yes       |                             |
+
+#### Notes on unmplemented functions
+
+* **eval()**: Is there ever a need to eval JS code from within Go?
+* **Number()**: This requires handling a bunch of corner cases which don't
+ normally exist in a strictly typed language such as Go. It seems that anyone
+ with a legitimate need for this function probably needs to write their own
+ wrapper to handle the cases that matter to them.
+* **parseInt()** and **parseFloat()**: These could be added, but doing so
+ will require answering some questions about the interfce. JavaScript has
+ effectively two relevant data types (int and float) where Go has has 12.
+ Deciding how to map JS's `parseInt()` to Go's `(u?)int(8|16|32|64)` types,
+ and JS's `parseFloat()` Go's `float(32|64)` or `complex(64|128)` needs to
+ be considered, as well as how to handle error cases (Go doesn't have a `NaN`
+ type, so any `NaN` result probably needs to be converted to a proper Go
+ error). If this matters to you, comments and/or PRs are welcome.
+
+### Installation and Usage
+Get or update this package and dependencies with:
+
+```
+go get -u -d -tags=js github.com/gopherjs/jsbuiltin
+```
+
+### Basic usage example
+
+This is a modified version of the Pet example in the main GopherJS documentation,
+to accept and return URI-encoded pet names using the jsbuiltin package.
+
+```go
+package main
+
+import (
+	"github.com/gopherjs/gopherjs/js"
+	"github.com/gopherjs/jsbuiltin"
+)
+
+func main() {
+	js.Global.Set("pet", map[string]interface{}{
+		"New": New,
+	})
+}
+
+type Pet struct {
+	name string
+}
+
+func New(name string) *js.Object {
+	return js.MakeWrapper(&Pet{name})
+}
+
+func (p *Pet) Name() string {
+	return jsbuiltin.EncodeURIComponent(p.name)
+}
+
+func (p *Pet) SetName(uriComponent string) error {
+	name, err := jsbuiltin.DecodeURIComponent(uriComponent)
+	if err != nil {
+		// Malformed UTF8 in uriComponent
+		return err
+	}
+	p.name = name
+	return nil
+}
+```