diff --git a/src/Tokenizer/Tokens.php b/src/Tokenizer/Tokens.php
index ac64fc03ca0..13b4aa44798 100644
--- a/src/Tokenizer/Tokens.php
+++ b/src/Tokenizer/Tokens.php
@@ -870,7 +870,7 @@ public function insertSlices(array $slices): void
         // that way we get around additional overhead this class adds with overridden offset* methods.
         foreach ($slices as $index => $slice) {
             if (!\is_int($index) || $index < 0) {
-                throw new \OutOfBoundsException(sprintf('Invalid index "%s"', $index));
+                throw new \OutOfBoundsException(sprintf('Invalid index "%s".', $index));
             }
 
             $slice = \is_array($slice) || $slice instanceof self ? $slice : [$slice];