diff --git a/module/VuFind/src/VuFind/Controller/CombinedController.php b/module/VuFind/src/VuFind/Controller/CombinedController.php
index 50832b8e8bfadb7758eb021833d43e78eb5b96c0..8f7bb0a43f56bf340a987f5200124ab0220ac53a 100644
--- a/module/VuFind/src/VuFind/Controller/CombinedController.php
+++ b/module/VuFind/src/VuFind/Controller/CombinedController.php
@@ -244,7 +244,14 @@ class CombinedController extends AbstractSearch
             $lookfor = $this->params()->fromQuery('lookfor');
             return $this->redirect()->toUrl($target . urlencode($lookfor));
         default:
-            throw new \Exception('Unexpected search type.');
+            // If parameters are completely missing, just redirect to home instead
+            // of throwing an error; this is possibly a misbehaving crawler that
+            // followed the SearchBox URL without passing any parameters.
+            if (empty($type) && empty($target)) {
+                return $this->redirect()->toRoute('home');
+            }
+            // If we have a weird value here, report it as an Exception:
+            throw new \Exception('Unexpected search type: "' . $type . '".');
         }
     }