diff --git a/php/OAuthSimple.php b/php/OAuthSimple.php
index 5d96276..645f961 100644
--- a/php/OAuthSimple.php
+++ b/php/OAuthSimple.php
@@ -297,6 +297,7 @@ class OAuthSimple {
         if (is_array($string))
             throw new OAuthSimpleException('Array passed to _oauthEscape');
         $string = urlencode($string);
+        $string = str_replace('+','%20',$string);
         $string = str_replace('!','%21',$string);
         $string = str_replace('*','%2A',$string);
         $string = str_replace('\'','%27',$string);