diff --git a/fixtures/glsl/index.js b/fixtures/glsl/index.js
new file mode 100644
index 0000000..fc929d7
--- /dev/null
+++ b/fixtures/glsl/index.js
@@ -0,0 +1,9 @@
+const glsl = require('glslify')
+
+console.log(glsl`
+precision mediump float;
+#pragma glslify: ones = require(./ones)
+void main () {
+  gl_FragColor = ones();
+}
+`)
diff --git a/fixtures/glsl/ones.glsl b/fixtures/glsl/ones.glsl
new file mode 100644
index 0000000..4cfd2bc
--- /dev/null
+++ b/fixtures/glsl/ones.glsl
@@ -0,0 +1,4 @@
+vec4 ones () {
+  return vec4(1);
+}
+#pragma glslify: export(ones)
diff --git a/fixtures/glsl/output.txt b/fixtures/glsl/output.txt
new file mode 100644
index 0000000..0dcae7a
--- /dev/null
+++ b/fixtures/glsl/output.txt
@@ -0,0 +1,12 @@
+
+precision mediump float;
+#define GLSLIFY 1
+#define GLSLIFY 1
+vec4 ones () {
+  return vec4(1);
+}
+
+void main () {
+  gl_FragColor = ones();
+}
+,
diff --git a/fixtures/glsl/package.json b/fixtures/glsl/package.json
new file mode 100644
index 0000000..b9b2970
--- /dev/null
+++ b/fixtures/glsl/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "fixture",
+  "version": "1.0.0",
+  "scripts": {
+    "build": "../../node_modules/.bin/webpack webpack.config.js"
+  },
+  "browserify": {
+    "transform": [
+      "glslify"
+    ]
+  }
+}
diff --git a/fixtures/glsl/webpack.config.js b/fixtures/glsl/webpack.config.js
new file mode 100644
index 0000000..475abc7
--- /dev/null
+++ b/fixtures/glsl/webpack.config.js
@@ -0,0 +1,15 @@
+const path = require('path')
+
+module.exports = {
+  entry: './index.js',
+  output: {
+    path: __dirname,
+    filename: 'bundle.js'
+  },
+  module: {
+    rules: [{
+      test: /\.js/,
+      use: path.join(__dirname, '..', '..')
+    }]
+  }
+}
diff --git a/index.js b/index.js
index af0f490..e88f84a 100644
--- a/index.js
+++ b/index.js
@@ -37,6 +37,7 @@ function loader (source) {
 
         const name = transform[0]
         const opts = transform[1] || {}
+        opts._flags = opts._flags || []
 
         if (typeof name === 'function') {
           return next(null, name(filename, opts))
diff --git a/package.json b/package.json
index 9f410f4..2f08538 100644
--- a/package.json
+++ b/package.json
@@ -20,13 +20,15 @@
   },
   "devDependencies": {
     "brfs": "^1.4.2",
+    "from2-string": "^1.1.0",
+    "glslify": "^6.1.0",
     "npm-which": "^2.0.0",
     "regl": "^1.3.0",
     "standard": "^5.4.1",
     "tap-spec": "^4.1.1",
     "tape": "^4.4.0",
     "through2": "^2.0.0",
-    "webpack": "^2.2.1"
+    "webpack": "^3.4.0"
   },
   "scripts": {
     "test": "node test.js | tspec",
diff --git a/test.js b/test.js
index 4c4ed3b..8afccfa 100644
--- a/test.js
+++ b/test.js
@@ -87,3 +87,39 @@ test('error handling', function (t) {
     t.equal(code, 2, 'exit code was 2')
   })
 })
+
+test('glsl-transform', function (t) {
+  const wpack = which.sync('webpack', { cwd: __dirname })
+  const output = path.join(__dirname, 'fixtures', 'glsl', 'bundle.js')
+  const config = path.join(__dirname, 'fixtures', 'glsl', 'webpack.config.js')
+  const fixture = path.join(__dirname, 'fixtures', 'glsl', 'output.txt')
+
+  t.plan(1)
+
+  try {
+    fs.unlinkSync(output)
+  } catch (e) {}
+
+  spawn(wpack, [
+    '--module-bind', 'js=' + __dirname,
+    '--config',
+    config
+  ], {
+    cwd: path.join(__dirname, 'fixtures', 'glsl'),
+    stdio: ['pipe', 'pipe', 2]
+  }).once('exit', function () {
+    const result = fs.readFileSync(output, { encoding: 'utf8' })
+
+    fs.unlinkSync(output)
+
+    vm.runInNewContext(result, {
+      console: {
+        log: function (shader) {
+          const expected = fs.readFileSync(fixture, { encoding: 'utf8' })
+          t.equal(shader + '\n', expected, 'processed brfs from package.json')
+        }
+      }
+    })
+  })
+})
+