diff --git a/src/messenger/webim/captcha.php b/src/messenger/webim/captcha.php
index b260775e..f17ab5c8 100644
--- a/src/messenger/webim/captcha.php
+++ b/src/messenger/webim/captcha.php
@@ -23,7 +23,7 @@ require_once('libs/common.php');
 require_once('libs/captcha.php');
 
 $captchaCode = gen_captcha();
-$_SESSION["captcha"] = $captchaCode;
+$_SESSION["mibew_captcha"] = $captchaCode;
 draw_captcha($captchaCode);
 
 exit;
diff --git a/src/messenger/webim/leavemessage.php b/src/messenger/webim/leavemessage.php
index b5363306..e891fd17 100644
--- a/src/messenger/webim/leavemessage.php
+++ b/src/messenger/webim/leavemessage.php
@@ -83,11 +83,11 @@ if( !$email ) {
 
 if($settings["enablecaptcha"] == "1" && can_show_captcha()) {
 	$captcha = getparam('captcha');
-	$original = isset($_SESSION['captcha']) ? $_SESSION['captcha'] : "";
+	$original = isset($_SESSION["mibew_captcha"]) ? $_SESSION["mibew_captcha"] : "";
 	if(empty($original) || empty($captcha) || $captcha != $original) {
 	  $errors[] = getlocal('errors.captcha');
 	}
-	unset($_SESSION['captcha']);
+	unset($_SESSION['mibew_captcha']);
 }
 
 if( count($errors) > 0 ) {