diff --git a/Assets/ImageManipulation.php b/Assets/ImageManipulation.php
index <HASH>..<HASH> 100644
--- a/Assets/ImageManipulation.php
+++ b/Assets/ImageManipulation.php
@@ -486,7 +486,7 @@ trait ImageManipulation {
 	 */
 	public function PreviewThumbnail() {
 		$width = (int)Config::inst()->get(get_class($this), 'asset_preview_width');
-		return $this->ScaleWidth($width)  ?: $this->IconTag();
+		return $this->ScaleMaxWidth($width)  ?: $this->IconTag();
 	}
 
 	/**
API PreviewThumbnail now uses ScaleMaxWidth

This will mean that if a thumbnail image is smaller than the preview_width defined, then it will no longer get blown up to the defined size.