diff --git a/src/lib/Server/Input/Parser/Criterion/Field.php b/src/lib/Server/Input/Parser/Criterion/Field.php
index 0df59bce..b68342da 100644
--- a/src/lib/Server/Input/Parser/Criterion/Field.php
+++ b/src/lib/Server/Input/Parser/Criterion/Field.php
@@ -76,7 +76,7 @@ private function getOperator($operatorName)
         if (!isset(self::OPERATORS[$operatorName])) {
             throw new Exceptions\Parser(
                 sprintf(
-                    'Unexpected Field operator, expected one of: %s',
+                    'Unexpected Field operator. Expected one of: %s',
                     implode(', ', array_keys(self::OPERATORS))
                 )
             );