diff --git a/README.md b/README.md
index f0bead9..e68a4a2 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@ Allows you to get the device pixel ratio using JavaScript.
 
 ## Size and delivery
 
-Currently, `getDevicePixelRatio.js` compresses to around 318 bytes (~0.3 KB), after minify and gzip. To minify, you might try these online tools: [Microsoft Ajax Minifier]:(http://ajaxmin.codeplex.com/), [Uglify]:(http://marijnhaverbeke.nl/uglifyjs), [Yahoo Compressor]:(http://refresh-sf.com/yui/), or [Closure Compiler](http://closure-compiler.appspot.com/home). Serve with gzip compression.
+Currently, `getDevicePixelRatio.js` compresses to around 221 bytes (~0.2 KB), after minify and gzip. To minify, you might try these online tools: [Microsoft Ajax Minifier](http://ajaxmin.codeplex.com/), [Uglify](http://marijnhaverbeke.nl/uglifyjs), [Yahoo Compressor](http://refresh-sf.com/yui/), or [Closure Compiler](http://closure-compiler.appspot.com/home). Serve with gzip compression.
 
 ## Sample
 
diff --git a/getDevicePixelRatio-min.js b/getDevicePixelRatio-min.js
index 3a6783d..11a466b 100644
--- a/getDevicePixelRatio-min.js
+++ b/getDevicePixelRatio-min.js
@@ -1,2 +1,2 @@
 /*! GetDevicePixelRatio | Author: Tyson Matanich, 2012 | License: MIT */
-(function(n){n.getDevicePixelRatio=function(){var t=1;return n.screen.systemXDPI!==undefined&&n.screen.logicalXDPI!==undefined&&n.screen.systemXDPI>n.screen.logicalXDPI?t=n.screen.systemXDPI/n.screen.logicalXDPI:n.devicePixelRatio!==undefined&&(t=n.devicePixelRatio),t}})(this);
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+(function(b){b.getDevicePixelRatio=function(){var a=b.screen||{},c=a.systemXDPI||1,a=a.logicalXDPI||1;return c>a?c/a:b.devicePixelRatio||1}})(this);
\ No newline at end of file
diff --git a/getDevicePixelRatio.js b/getDevicePixelRatio.js
index 59358d8..c3d65e2 100644
--- a/getDevicePixelRatio.js
+++ b/getDevicePixelRatio.js
@@ -1,15 +1,14 @@
 /*! GetDevicePixelRatio | Author: Tyson Matanich, 2012 | License: MIT */
 (function (window) {
+	// device pixel ratio even before dom ready
+	// http://stackoverflow.com/a/29913175
 	window.getDevicePixelRatio = function () {
-		var ratio = 1;
-		// To account for zoom, change to use deviceXDPI instead of systemXDPI
-		if (window.screen.systemXDPI !== undefined && window.screen.logicalXDPI !== undefined && window.screen.systemXDPI > window.screen.logicalXDPI) {
-			// Only allow for values > 1
-			ratio = window.screen.systemXDPI / window.screen.logicalXDPI;
-		}
-		else if (window.devicePixelRatio !== undefined) {
-			ratio = window.devicePixelRatio;
-		}
-		return ratio;
+		var screen = window.screen || {};
+		var systemXDPI = screen.systemXDPI || 1;
+		var logicalXDPI = screen.logicalXDPI || 1;
+		// To account for zoom, change to deviceXDPI instead of systemXDPI
+		if (systemXDPI > logicalXDPI) return systemXDPI / logicalXDPI;
+		// Fall back to legacy devicePixelRatio or return 1
+		else return window.devicePixelRatio || 1;
 	};
 })(this);
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