diff --git a/lib/Twitter/Text/HitHighlighter.php b/lib/Twitter/Text/HitHighlighter.php
index a68bd26..97bad52 100644
--- a/lib/Twitter/Text/HitHighlighter.php
+++ b/lib/Twitter/Text/HitHighlighter.php
@@ -141,7 +141,7 @@ public function highlight($tweet = null, array $hits = null)
             $offset = 0;
             $start_in_chunk = false;
             # Flatten the multidimensional hits array:
-            $hits_flat = array_merge(...array_values($hits));
+            $hits_flat = call_user_func_array('array_merge', array_values($hits));
             $hits_flat_count = count($hits_flat);
             # Loop over the hit indices:
             for ($index = 0; $index < $hits_flat_count; $index++) {