diff --git a/context_reaction_http_header.inc b/context_reaction_http_header.inc
index edb2725..26d2fd5 100755
--- a/context_reaction_http_header.inc
+++ b/context_reaction_http_header.inc
@@ -16,6 +16,10 @@ class context_reaction_http_header extends context_reaction {
 
     // Get set values from the context for these hooks
     foreach ($items_from_hook as $header => $item) {
+      if (!isset($values['http_header'][$header])) {
+        $items_from_hook[$header]['#default_value'] = '';
+        continue;
+      }
       $items_from_hook[$header]['#default_value'] = $values['http_header'][$header];
     }