diff --git a/core/modules/responsive_image/responsive_image.module b/core/modules/responsive_image/responsive_image.module
index a5e1d0d..244e904 100644
--- a/core/modules/responsive_image/responsive_image.module
+++ b/core/modules/responsive_image/responsive_image.module
@@ -238,7 +238,7 @@ function theme_responsive_image($variables) {
       ksort($srcset);
       $sources[] = array(
         '#theme' => 'responsive_image_source',
-        '#srcset' => array_unique($srcset),
+        '#srcset' => array_map('unserialize', array_unique(array_map('serialize', $srcset))),
         '#media' => $breakpoint->getMediaQuery(),
         // Only set a MIME type if all derivative images have the same MIME type.
         '#mime_type' => count(array_unique($derivative_mime_types)) == 1 ? $derivative_mime_types[0] : '',