diff --git a/jquery.backgroundSize.js b/jquery.backgroundSize.js
index 7417632..4baa6ed 100644
--- a/jquery.backgroundSize.js
+++ b/jquery.backgroundSize.js
@@ -178,8 +178,12 @@ $.refreshBackground = function( elem ) {
 		imgDim = $.data( elem, "bgsImgDim" ),
 		$img = $( $.data( elem, "bgsImg" ) ),
 		pos = $.data( elem, "bgsPos" ),
-		prevConstrain = $.data( elem, "bgsConstrain" ),
-		currConstrain,
+		prevConstrain = $.data( elem, "bgsConstrain" );
+
+	if (!elemDim || !imgDim)
+		return;
+
+	var currConstrain,
 		elemRatio = elemDim.width / elemDim.height,
 		imgRatio = imgDim.width / imgDim.height,
 		delta;