diff --git a/core/lib/Drupal/Core/Database/Statement.php b/core/lib/Drupal/Core/Database/Statement.php
index ca70c4c..418c327 100644
--- a/core/lib/Drupal/Core/Database/Statement.php
+++ b/core/lib/Drupal/Core/Database/Statement.php
@@ -123,7 +123,7 @@ public function rowCount() {
       return parent::rowCount();
     }
     else {
-      throw new RowCountException();
+      throw new RowCountException('rowCount() is not allowed for SELECT queries. Query: ' . $this->getQueryString());
     }
   }
 
diff --git a/core/lib/Drupal/Core/Database/StatementEmpty.php b/core/lib/Drupal/Core/Database/StatementEmpty.php
index e6cd08d..8f4b8c4 100644
--- a/core/lib/Drupal/Core/Database/StatementEmpty.php
+++ b/core/lib/Drupal/Core/Database/StatementEmpty.php
@@ -40,7 +40,7 @@ public function rowCount() {
     if ($this->allowRowCount) {
       return 0;
     }
-    throw new RowCountException();
+    throw new RowCountException('rowCount() is not allowed for SELECT queries.');
   }
 
   public function setFetchMode($mode, $a1 = NULL, $a2 = array()) {