diff --git a/src/Reports/ElementTypeReport.php b/src/Reports/ElementTypeReport.php
index c77e1214..cb9d1aa1 100644
--- a/src/Reports/ElementTypeReport.php
+++ b/src/Reports/ElementTypeReport.php
@@ -62,7 +62,8 @@ protected function getElementTypes()
 
     public function columns()
     {
-        $inUseReport = new ElementsInUseReport;
+        // Get from Injector so substitutions are used...
+        $inUseReport = ElementsInUseReport::singleton();
 
         return [
             'Icon' => [
@@ -73,7 +74,9 @@ public function columns()
                 'formatting' => function ($value, $item) use ($inUseReport) {
                     return sprintf(
                         '<a class="grid-field__link" href="%s" title="%s">%s</a>',
-                        $inUseReport->getLink('?filters[ClassName]='. $item->ClassName),
+                        $inUseReport->getLink(
+                            '?filters[' . $inUseReport::CLASS_NAME_FILTER_KEY . ']=' . $item->ClassName
+                        ),
                         $item->Type,
                         $item->TypeNice
                     );
diff --git a/src/Reports/ElementsInUseReport.php b/src/Reports/ElementsInUseReport.php
index f52f1676..1d15adaf 100644
--- a/src/Reports/ElementsInUseReport.php
+++ b/src/Reports/ElementsInUseReport.php
@@ -11,6 +11,11 @@
 
 class ElementsInUseReport extends Report
 {
+    /**
+     * The string used in GET params to filter the records in this report by element type
+     */
+    const CLASS_NAME_FILTER_KEY = 'ClassName';
+
     public function title()
     {
         return _t(__CLASS__ . '.ReportTitle', 'Content blocks in use');
@@ -21,8 +26,8 @@ public function sourceRecords($params = [])
         /** @var DataList $elements */
         $elements = BaseElement::get()->exclude(['ClassName' => BaseElement::class]);
 
-        if (isset($params['ClassName'])) {
-            $className = $this->unsanitiseClassName($params['ClassName']);
+        if (isset($params[static::CLASS_NAME_FILTER_KEY])) {
+            $className = $this->unsanitiseClassName($params[static::CLASS_NAME_FILTER_KEY]);
             $elements = $elements->filter(['ClassName' => $className]);
         }
 
@@ -122,7 +127,7 @@ public function getBreadcrumbs()
 
         // Only apply breadcrumbs if a "ClassName" filter is applied. This implies that we came from the
         // "element type report".
-        if (!isset($params['ClassName'])) {
+        if (!isset($params[static::CLASS_NAME_FILTER_KEY])) {
             return [];
         }