diff --git a/lib/index.js b/lib/index.js
index 338bf9b..c9e7e5f 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -64,6 +64,9 @@ exports.get = function(path, o, special, map) {
 
   for (var i = 0; i < parts.length; ++i) {
     part = parts[i];
+    if (typeof parts[i] !== 'string' && typeof parts[i] !== 'number') {
+      throw new TypeError('Each segment of path to `get()` must be a string or number, got ' + typeof parts[i]);
+    }
 
     if (Array.isArray(obj) && !/^\d+$/.test(part)) {
       // reading a property from the array items
@@ -112,6 +115,9 @@ exports.has = function(path, o) {
   var len = parts.length;
   var cur = o;
   for (var i = 0; i < len; ++i) {
+    if (typeof parts[i] !== 'string' && typeof parts[i] !== 'number') {
+      throw new TypeError('Each segment of path to `has()` must be a string or number, got ' + typeof parts[i]);
+    }
     if (cur == null || typeof cur !== 'object' || !(parts[i] in cur)) {
       return false;
     }
@@ -143,6 +149,9 @@ exports.unset = function(path, o) {
     if (cur == null || typeof cur !== 'object' || !(parts[i] in cur)) {
       return false;
     }
+    if (typeof parts[i] !== 'string' && typeof parts[i] !== 'number') {
+      throw new TypeError('Each segment of path to `unset()` must be a string or number, got ' + typeof parts[i]);
+    }
     // Disallow any updates to __proto__ or special properties.
     if (ignoreProperties.indexOf(parts[i]) !== -1) {
       return false;
@@ -193,6 +202,9 @@ exports.set = function(path, val, o, special, map, _copying) {
   if (null == o) return;
 
   for (var i = 0; i < parts.length; ++i) {
+    if (typeof parts[i] !== 'string' && typeof parts[i] !== 'number') {
+      throw new TypeError('Each segment of path to `set()` must be a string or number, got ' + typeof parts[i]);
+    }
     // Silently ignore any updates to `__proto__`, these are potentially
     // dangerous if using mpath with unsanitized data.
     if (ignoreProperties.indexOf(parts[i]) !== -1) {