diff --git a/lib/buffer.js b/lib/buffer.js
index ca4fedf517..3378dcebfc 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -30,7 +30,7 @@ SlowBuffer.prototype.__proto__ = Buffer.prototype;
 
 
 function clamp(index, len, defaultValue) {
-  if (typeof index === 'undefined') return defaultValue;
+  if (typeof index !== 'number') return defaultValue;
   index = ~~index;  // Coerce to integer.
   if (index >= len) return len;
   if (index >= 0) return index;
@@ -49,7 +49,7 @@ function toHex(n) {
 SlowBuffer.prototype.toString = function(encoding, start, end) {
   encoding = String(encoding || 'utf8').toLowerCase();
   start = +start || 0;
-  if (typeof end == 'undefined') end = this.length;
+  if (typeof end !== 'number') end = this.length;
 
   // Fastpath empty strings
   if (+end == start) {
@@ -150,15 +150,6 @@ SlowBuffer.prototype.slice = function(start, end) {
 };
 
 
-function coerce(length) {
-  // Coerce length to a number (possibly NaN), round up
-  // in case it's fractional (e.g. 123.456). Since NaN
-  // comparisons are always false, use to return zero.
-  length = Math.ceil(+length);
-  return length > 0 ? length : 0;
-}
-
-
 var zeroBuffer = new SlowBuffer(0);
 
 // Buffer
@@ -175,22 +166,22 @@ function Buffer(subject, encoding, offset) {
       throw new TypeError('First argument must be a Buffer when slicing');
     }
 
-    this.length = coerce(encoding);
+    this.length = +encoding > 0 ? Math.ceil(encoding) : 0;
     this.parent = subject.parent ? subject.parent : subject;
     this.offset = offset;
   } else {
     // Find the length
     switch (type = typeof subject) {
       case 'number':
-        this.length = coerce(subject);
+        this.length = +subject > 0 ? Math.ceil(subject) : 0;
         break;
 
       case 'string':
         this.length = Buffer.byteLength(subject, encoding);
         break;
 
-      case 'object': // Assume object is an array
-        this.length = coerce(subject.length);
+      case 'object': // Assume object is array-ish
+        this.length = +subject.length > 0 ? Math.ceil(subject.length) : 0;
         break;
 
       default:
@@ -217,14 +208,24 @@ function Buffer(subject, encoding, offset) {
       this.offset = 0;
     }
 
-    // Treat array-ish objects as a byte array.
-    if (isArrayIsh(subject)) {
-      for (var i = 0; i < this.length; i++) {
-        this.parent[i + this.offset] = subject[i];
+    // optimize by branching logic for new allocations
+    if (typeof subject !== 'number') {
+      if (type === 'string') {
+        // We are a string
+        this.length = this.write(subject, 0, encoding);
+      // if subject is buffer then use built-in copy method
+      } else if (Buffer.isBuffer(subject)) {
+        if (subject.parent)
+          subject.parent.copy(this.parent,
+                              this.offset,
+                              subject.offset,
+                              this.length + subject.offset);
+        else
+          subject.copy(this.parent, this.offset, 0, this.length);
+      } else if (isArrayIsh(subject)) {
+        for (var i = 0; i < this.length; i++)
+          this.parent[i + this.offset] = subject[i];
       }
-    } else if (type == 'string') {
-      // We are a string
-      this.length = this.write(subject, 0, encoding);
     }
   }
 
@@ -232,7 +233,7 @@ function Buffer(subject, encoding, offset) {
 }
 
 function isArrayIsh(subject) {
-  return Array.isArray(subject) || Buffer.isBuffer(subject) ||
+  return Array.isArray(subject) ||
          subject && typeof subject === 'object' &&
          typeof subject.length === 'number';
 }
@@ -388,13 +389,13 @@ Buffer.prototype.toJSON = function() {
 Buffer.prototype.toString = function(encoding, start, end) {
   encoding = String(encoding || 'utf8').toLowerCase();
 
-  if (typeof start == 'undefined' || start < 0) {
+  if (typeof start !== 'number' || start < 0) {
     start = 0;
   } else if (start > this.length) {
     start = this.length;
   }
 
-  if (typeof end == 'undefined' || end > this.length) {
+  if (typeof end !== 'number' || end > this.length) {
     end = this.length;
   } else if (end < 0) {
     end = 0;
@@ -445,7 +446,7 @@ Buffer.prototype.fill = function fill(value, start, end) {
   if (typeof value === 'string') {
     value = value.charCodeAt(0);
   }
-  if (!(typeof value === 'number') || isNaN(value)) {
+  if (typeof value !== 'number' || isNaN(value)) {
     throw new TypeError('value is not a number');
   }