diff --git a/README.md b/README.md
index 71b8990..15a2334 100644
--- a/README.md
+++ b/README.md
@@ -622,8 +622,9 @@ s('bàř')->prepend('fòô'); // 'fòôbàř'
 
 Replaces all occurrences of $pattern in $str by $replacement. An alias
 for mb_ereg_replace(). Note that the 'i' option with multibyte patterns
-in mb_ereg_replace() requires PHP 5.4+. This is due to a lack of support
-in the bundled version of Oniguruma in PHP 5.3.
+in mb_ereg_replace() requires PHP 5.6+ for correct results. This is due
+to a lack of support in the bundled version of Oniguruma in PHP < 5.6,
+and current versions of HHVM (3.8 and below).
 
 ```php
 s('fòô ')->regexReplace('f[òô]+\s', 'bàř', 'msr'); // 'bàř'
diff --git a/src/Stringy.php b/src/Stringy.php
index ea44539..4a3fbe9 100644
--- a/src/Stringy.php
+++ b/src/Stringy.php
@@ -943,8 +943,9 @@ class Stringy implements \Countable, \IteratorAggregate, \ArrayAccess
     /**
      * Replaces all occurrences of $pattern in $str by $replacement. An alias
      * for mb_ereg_replace(). Note that the 'i' option with multibyte patterns
-     * in mb_ereg_replace() requires PHP 5.4+. This is due to a lack of support
-     * in the bundled version of Oniguruma in PHP 5.3.
+     * in mb_ereg_replace() requires PHP 5.6+ for correct results. This is due
+     * to a lack of support in the bundled version of Oniguruma in PHP < 5.6,
+     * and current versions of HHVM (3.8 and below).
      *
      * @param  string  $pattern     The regular expression pattern
      * @param  string  $replacement The string to replace with
@@ -1183,7 +1184,8 @@ class Stringy implements \Countable, \IteratorAggregate, \ArrayAccess
             return array();
         }
 
-        // mb_split errors when supplied an empty pattern in PHP 5.3
+        // mb_split errors when supplied an empty pattern in < PHP 5.4.13
+        // and current versions of HHVM (3.8 and below)
         if ($pattern === '') {
             return array(static::create($this->str, $this->encoding));
         }