Provide explicit error message about bad input

index.js

@@ -9,6 +9,7 @@ var isglob = require('is-glob');
 var arrify = require('arrify');
 var isAbsolute = require('path-is-absolute');
 var flatten = require('lodash.flatten');
+var isString = require('is-string');
 
 var NodeFsHandler = require('./lib/nodefs-handler');
 var FsEventsHandler = require('./lib/fsevents-handler');
@@ -474,6 +475,10 @@ FSWatcher.prototype.add = function(paths, _origAdd, _internal) {
   this.closed = false;
   paths = flatten(arrify(paths));
 
+  if (!paths.every(isString)) {
+    throw new TypeError('Non-string provided as watch path');
+  }
+
   if (cwd) paths = paths.map(function(path) {
     if (isAbsolute(path)) {
       return path;

package.json

@@ -47,6 +47,7 @@
     "glob-parent": "^2.0.0",
     "is-binary-path": "^1.0.0",
     "is-glob": "^2.0.0",
+    "is-string": "^1.0.4",
     "lodash.flatten": "^3.0.2",
     "path-is-absolute": "^1.0.0",
     "readdirp": "^2.0.0"