diff --git a/modules/image/image.field.inc b/modules/image/image.field.inc
index f41df500f1a41e7c9fd862da7f8bbc1c758a71f3..9e276af761dcd6d3790a3277d4cf86d9f1767635 100644
--- a/modules/image/image.field.inc
+++ b/modules/image/image.field.inc
@@ -465,7 +465,7 @@ function image_field_formatter_view($entity_type, $entity, $field, $instance, $l
 
   // Check if the formatter involves a particular image style.
   $matches = array();
-  if (preg_match('/__([a-z0-9_]+)/', $display['type'], $matches)) {
+  if (preg_match('/__([a-z0-9_-]+)/', $display['type'], $matches)) {
     $image_style = $matches[1];
   }