diff --git a/lib/Horde/Form/Type.php b/lib/Horde/Form/Type.php
index b63c65b..3175d1d 100644
--- a/lib/Horde/Form/Type.php
+++ b/lib/Horde/Form/Type.php
@@ -1570,7 +1570,7 @@ public function loadImageData($image)
     public function getRandomId()
     {
         if (!isset($this->_random)) {
-            $this->_random = uniqid(mt_rand());
+            $this->_random = uniqid((string)mt_rand());
         }
         return $this->_random;
     }
diff --git a/src/V3/ImageVariable.php b/src/V3/ImageVariable.php
index cafa991..13812df 100644
--- a/src/V3/ImageVariable.php
+++ b/src/V3/ImageVariable.php
@@ -458,7 +458,7 @@ public function loadImageData($image)
     public function getRandomId()
     {
         if (!isset($this->_random)) {
-            $this->_random = uniqid(mt_rand());
+            $this->_random = uniqid((string)mt_rand());
         }
 
         return $this->_random;