diff --git a/index.js b/index.js
index f751cef..880f1f0 100644
--- a/index.js
+++ b/index.js
@@ -60,7 +60,7 @@ const defaultOptions = {
   },
 }
 
-const getBrowserifyOptions = (entry, userBrowserifyOptions = {}, typescriptPath = null) => {
+const getBrowserifyOptions = async (entry, userBrowserifyOptions = {}, typescriptPath = null) => {
   let browserifyOptions = cloneDeep(defaultOptions.browserifyOptions)
 
   // allow user to override default options
@@ -82,6 +82,16 @@ const getBrowserifyOptions = (entry, userBrowserifyOptions = {}, typescriptPath
   })
 
   if (typescriptPath) {
+    if (typeof typescriptPath !== 'string') {
+      throw new Error(`The 'typescript' option must be a string. You passed: ${typescriptPath}`)
+    }
+
+    const pathExists = await fs.pathExists(typescriptPath)
+
+    if (!pathExists) {
+      throw new Error(`The 'typescript' option must be a valid path to your TypeScript installation. We could not find anything at the following path: ${typescriptPath}`)
+    }
+
     const transform = browserifyOptions.transform
     const hasTsifyTransform = transform.some(([name]) => name.includes('tsify'))
     const hastsifyPlugin = browserifyOptions.plugin.includes('tsify')
@@ -135,7 +145,7 @@ const preprocessor = (options = {}) => {
   // when running in the GUI, it will likely get called multiple times
   // with the same filePath, as the user could re-run the tests, causing
   // the supported file and spec file to be requested again
-  return (file) => {
+  return async (file) => {
     const filePath = file.filePath
 
     debug('get:', filePath)
@@ -157,7 +167,7 @@ const preprocessor = (options = {}) => {
     debug('input:', filePath)
     debug('output:', outputPath)
 
-    const browserifyOptions = getBrowserifyOptions(filePath, options.browserifyOptions, options.typescript)
+    const browserifyOptions = await getBrowserifyOptions(filePath, options.browserifyOptions, options.typescript)
     const watchifyOptions = Object.assign({}, defaultOptions.watchifyOptions, options.watchifyOptions)
 
     const bundler = browserify(browserifyOptions)
diff --git a/test/unit/index_spec.js b/test/unit/index_spec.js
index be99068..5b729f5 100644
--- a/test/unit/index_spec.js
+++ b/test/unit/index_spec.js
@@ -424,23 +424,55 @@ describe('browserify preprocessor', function () {
         })
       })
 
-      describe('when typescript path and tsify are given together', function () {
-        it('throws error when it is a plugin', function () {
+      describe('validation', function () {
+        const shouldntResolve = () => {
+          throw new Error('Should error, should not resolve')
+        }
+
+        it('throws error when typescript path is not a string', function () {
+          this.options.typescript = true
+
+          return this.run()
+          .then(shouldntResolve)
+          .catch((err) => {
+            expect(err.message).to.equal(`The 'typescript' option must be a string. You passed: true`)
+          })
+        })
+
+        it('throws error when nothing exists at typescript path', function () {
+          this.options.typescript = '/nothing/here'
+
+          return this.run()
+          .then(shouldntResolve)
+          .catch((err) => {
+            expect(err.message).to.equal(`The 'typescript' option must be a valid path to your TypeScript installation. We could not find anything at the following path: /nothing/here`)
+          })
+        })
+
+        it('throws error when typescript path and tsify plugin are specified', function () {
           this.options.browserifyOptions = {
             plugin: ['tsify'],
           }
 
-          expect(this.run).to.throw('This may cause conflicts')
+          return this.run()
+          .then(shouldntResolve)
+          .catch((err) => {
+            expect(err.message).to.include('This may cause conflicts')
+          })
         })
 
-        it('throws error when it is a transform', function () {
+        it('throws error when typescript path and tsify transform are specified', function () {
           this.options.browserifyOptions = {
             transform: [
               ['path/to/tsify', {}],
             ],
           }
 
-          expect(this.run).to.throw('This may cause conflicts')
+          return this.run()
+          .then(shouldntResolve)
+          .catch((err) => {
+            expect(err.message).to.include('This may cause conflicts')
+          })
         })
       })
     })