diff --git a/Parsedown.php b/Parsedown.php
index 8355d53..918b4af 100755
--- a/Parsedown.php
+++ b/Parsedown.php
@@ -1068,23 +1068,23 @@ class Parsedown
     # Read-only
 
     private static $strong_regex = array(
-        '*' => '/^[*]{2}([^*]+?)[*]{2}(?![*])/s',
-        '_' => '/^__([^_]+?)__(?!_)/s',
+        '*' => '/^[*]{2}([^*]+?)[*]{2}(?![*])/us',
+        '_' => '/^__([^_]+?)__(?!_)/us',
     );
 
     private static $em_regex = array(
-        '*' => '/^[*]([^*]+?)[*](?![*])/s',
-        '_' => '/^_([^_]+?)[_](?![_])\b/s',
+        '*' => '/^[*]([^*]+?)[*](?![*])/us',
+        '_' => '/^_([^_]+?)[_](?![_])\b/us',
     );
 
     private static $strong_em_regex = array(
-        '*' => '/^[*]{2}(.*?)[*](.+?)[*](.*?)[*]{2}/s',
-        '_' => '/^__(.*?)_(.+?)_(.*?)__/s',
+        '*' => '/^[*]{2}(.*?)[*](.+?)[*](.*?)[*]{2}/us',
+        '_' => '/^__(.*?)_(.+?)_(.*?)__/us',
     );
 
     private static $em_strong_regex = array(
-        '*' => '/^[*](.*?)[*]{2}(.+?)[*]{2}(.*?)[*]/s',
-        '_' => '/^_(.*?)__(.+?)__(.*?)_/s',
+        '*' => '/^[*](.*?)[*]{2}(.+?)[*]{2}(.*?)[*]/us',
+        '_' => '/^_(.*?)__(.+?)__(.*?)_/us',
     );
 
     private static $special_characters = array(
@@ -1102,4 +1102,4 @@ class Parsedown
                           'span',
                           'time',
     );
-}
\ No newline at end of file
+}