diff --git a/.gitignore b/.gitignore
index 96978ba..bd3452d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@ npm-debug.log*
 
 #ignore node_modules, as the node project is not "deployed" per se: http://www.mikealrogers.com/posts/nodemodules-in-git.html
 /node_modules
+.DS_Store
diff --git a/lib/quibble.js b/lib/quibble.js
index 83d8c8c..1351774 100644
--- a/lib/quibble.js
+++ b/lib/quibble.js
@@ -2,6 +2,7 @@ var Module = require('module')
 var path = require('path')
 var { URL } = require('url')
 var resolve = require('resolve')
+var { accessSync, constants } = require('fs')
 var _ = {
   compact: require('lodash/fp/compact'),
   extendAll: require('lodash/fp/extendAll'),
@@ -93,6 +94,7 @@ quibble.esm = async function (importPath, namedExportStubs, defaultExportStub) {
     : isAbsolutePath
       ? importPath
       : path.resolve(path.dirname(callerFile), importPath)
+  accessSync(fullModulePath, constants.R_OK)
 
   global.__quibble.quibbledModules.set(fullModulePath, {
     defaultExportStub,