diff --git a/src/flextype/Foundation/Entries/Fields/PublishedAtField.php b/src/flextype/Foundation/Entries/Fields/PublishedAtField.php
index ba68d3b6..4421531b 100644
--- a/src/flextype/Foundation/Entries/Fields/PublishedAtField.php
+++ b/src/flextype/Foundation/Entries/Fields/PublishedAtField.php
@@ -12,7 +12,7 @@ if (flextype('registry')->get('flextype.settings.entries.fields.published_at.ena
         if (flextype('entries')->getStorage('fetch_single.data.published_at') == null) {
             flextype('entries')->setStorage('fetch_single.data.published_at', (int) flextype('filesytem')->file(flextype('entries')->getFileLocation(flextype('entries')->getStorage('fetch_single.id')))->lastModified());
         } else {
-            flextype('entries')->setStorage('fetch_single.data.published_at', (int) strtotime(flextype('entries')->getStorage('fetch_single.data.published_at')));
+            flextype('entries')->setStorage('fetch_single.data.published_at', (int) strtotime((string) flextype('entries')->getStorage('fetch_single.data.published_at')));
         }
     });