diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index a7118bf..1c6e76b 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -209,7 +209,9 @@
 	if (extension_loaded('mbstring'))
 	{
 		define('MB_ENABLED', TRUE);
-		ini_set('mbstring.internal_encoding', $charset);
+		// mbstring.internal_encoding is deprecated starting with PHP 5.6
+		// and it's usage triggers E_DEPRECATED messages.
+		@ini_set('mbstring.internal_encoding', $charset);
 		// This is required for mb_convert_encoding() to strip invalid characters.
 		// That's utilized by CI_Utf8, but it's also done for consistency with iconv.
 		mb_substitute_character('none');
diff --git a/tests/Bootstrap.php b/tests/Bootstrap.php
index 195fc0d..cc84abf 100644
--- a/tests/Bootstrap.php
+++ b/tests/Bootstrap.php
@@ -46,7 +46,7 @@
 if (extension_loaded('mbstring'))
 {
 	defined('MB_ENABLED') OR define('MB_ENABLED', TRUE);
-	ini_set('mbstring.internal_encoding', 'UTF-8');
+	@ini_set('mbstring.internal_encoding', 'UTF-8');
 	mb_substitute_character('none');
 }
 else