diff --git a/service.inc b/service.inc
index 61a8120..d305448 100644
--- a/service.inc
+++ b/service.inc
@@ -1036,9 +1036,9 @@ class SearchApiDbService extends SearchApiAbstractService {
             // Check for over-long tokens.
             $score = $v['score'];
             $v = $v['value'];
-            if (strlen($v) > 50) {
+            if (drupal_strlen($v) > 50) {
               $words = preg_split('/[^\p{L}\p{N}]+/u', $v, -1, PREG_SPLIT_NO_EMPTY);
-              if (count($words) > 1 && max(array_map('strlen', $words)) <= 50) {
+              if (count($words) > 1 && max(array_map('drupal_strlen', $words)) <= 50) {
                 // Overlong token is due to bad tokenizing.
                 // Check for "Tokenizer" preprocessor on index.
                 if (empty($index->options['processors']['search_api_tokenizer']['status'])) {