diff --git a/CHANGELOG-0.x.md b/CHANGELOG-0.x.md
index ca7a976..6d13f0d 100644
--- a/CHANGELOG-0.x.md
+++ b/CHANGELOG-0.x.md
@@ -1,6 +1,8 @@
 # CHANGELOG for 0.x
 This changelog references the relevant changes done in 0.x versions.
 
+## v0.3.1
+* BUG :: Fix invalid string casting on Numbr in ElasticaQueryBuilder.
 
 ## v0.3.0
 __BREAKING CHANGES__
diff --git a/src/Builder/ElasticaQueryBuilder.php b/src/Builder/ElasticaQueryBuilder.php
index 85b2e3c..4bbd09e 100755
--- a/src/Builder/ElasticaQueryBuilder.php
+++ b/src/Builder/ElasticaQueryBuilder.php
@@ -451,7 +451,7 @@ protected function addTermToQuery(string $method, Node $node, ?Field $field = nu
             return;
         }
 
-        $value = $this->lowerCaseTerms ? strtolower((string)$node->getValue()) : $node->getValue();
+        $value = $this->lowerCaseTerms && !$node instanceof Numbr ? strtolower((string)$node->getValue()) : $node->getValue();
         $fieldName = $this->inField() ? $field->getName() : $this->defaultFieldName;
 
         if ($this->inField() && !$this->inSubquery()) {