diff --git a/ckanext/textpreview/plugin.py b/ckanext/textpreview/plugin.py
index 407fa52d7c9..32209d2cb98 100644
--- a/ckanext/textpreview/plugin.py
+++ b/ckanext/textpreview/plugin.py
@@ -63,7 +63,7 @@ def configure(self, config):
 
     def can_preview(self, data_dict):
         resource = data_dict['resource']
-        format_lower = resource['format'].lower()
+        format_lower = resource.get('format', '').lower()
 
         quality = QUALITY.get(format_lower, 1)