diff --git a/src/Aggregation/Bucketing/HistogramAggregation.php b/src/Aggregation/Bucketing/HistogramAggregation.php
index 5fc98c2f2582cb72c58cb56d83421c14b55a0d24..3a7cf9723204754f321384aae796da4c060a84d4 100644
--- a/src/Aggregation/Bucketing/HistogramAggregation.php
+++ b/src/Aggregation/Bucketing/HistogramAggregation.php
@@ -184,7 +184,8 @@ class HistogramAggregation extends AbstractAggregation
             [
                 'min' => $min,
                 'max' => $max,
-            ]
+            ],
+            'strlen'
         );
         $this->extendedBounds = $bounds;
     }