diff --git a/src/Monolog/Processor/IntrospectionProcessor.php b/src/Monolog/Processor/IntrospectionProcessor.php
index 8e65811d..56debfd5 100644
--- a/src/Monolog/Processor/IntrospectionProcessor.php
+++ b/src/Monolog/Processor/IntrospectionProcessor.php
@@ -91,7 +91,7 @@ class IntrospectionProcessor
         return $record;
     }
 
-    private function isTraceClassOrSkippedFunction ($trace, $index)
+    private function isTraceClassOrSkippedFunction (array $trace, $index)
     {
         if (isset($trace[$index]) === false) {
             return false;