diff --git a/lib/array.js b/lib/array.js
index 50211ee..9262e0f 100644
--- a/lib/array.js
+++ b/lib/array.js
@@ -35,7 +35,6 @@ function at(a, i) {
   return a[a.length + i];
 }
 
-// TODO make this work for non-array objects
 function compact(a) {
   var b = []
     , i = a.length
@@ -50,10 +49,17 @@ function first(a) { return a[0]; }
 
 // Based on underscore.js's flatten
 function flatten(a) {
-  return a.reduce(function(initial, elem) {
-    if (elem && elem.flatten) initial = initial.concat(elem.flatten());
-    else initial.push(elem);
-    return initial;
+  return a.reduce(function(flat, val) {
+    if (val && typeof val.flatten === 'function') {
+      flat = flat.concat(val.flatten());
+    }
+    else if (Array.isArray(val)) {
+      flat = flat.concat(flatten(val));
+    }
+    else {
+      flat.push(val);
+    }
+    return flat;
   });
 }