diff --git a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Search/FacetsResponse.php b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Search/FacetsResponse.php
index 55503d50d6..42c5a63e25 100644
--- a/lib/Alchemy/Phrasea/SearchEngine/Elastic/Search/FacetsResponse.php
+++ b/lib/Alchemy/Phrasea/SearchEngine/Elastic/Search/FacetsResponse.php
@@ -46,22 +46,23 @@ class FacetsResponse
                 if (!isset($bucket['key']) || !isset($bucket['doc_count'])) {
                     $this->throwAggregationResponseError();
                 }
+                $key = array_key_exists('key_as_string', $bucket) ? $bucket['key_as_string'] : $bucket['key'];
                 if($tf) {
                     // the field is one of the hardcoded tech fields
                     $value = [
-                        'value'     => $valueFormatter($bucket['key']),
-                        'raw_value' => $bucket['key'],
+                        'value'     => $valueFormatter($key),
+                        'raw_value' => $key,
                         'count'     => $bucket['doc_count'],
-                        'query'     => sprintf($tf['query'], $this->escaper->escapeWord($bucket['key']))
+                        'query'     => sprintf($tf['query'], $this->escaper->escapeWord($key))
                     ];
                 }
                 else {
                     // the field is a normal field
                     $value = [
-                        'value'     => $bucket['key'],
-                        'raw_value' => $bucket['key'],
+                        'value'     => $key,
+                        'raw_value' => $key,
                         'count'     => $bucket['doc_count'],
-                        'query'     => sprintf('field.%s:%s', $this->escaper->escapeWord($name), $this->escaper->escapeWord($bucket['key']))
+                        'query'     => sprintf('field.%s:%s', $this->escaper->escapeWord($name), $this->escaper->escapeWord($key))
                     ];
                 }