diff --git a/system/src/Grav/Common/Assets.php b/system/src/Grav/Common/Assets.php
index 50e4ba4a2..16822b990 100644
--- a/system/src/Grav/Common/Assets.php
+++ b/system/src/Grav/Common/Assets.php
@@ -413,7 +413,7 @@ class Assets
         }
 
         $key = md5($asset);
-        if (is_string($asset) && !array_key_exists($key, $this->inline_css)) {
+        if ($asset && is_string($asset) && !array_key_exists($key, $this->inline_css)) {
             $this->inline_css[$key] = $data;
         }
 
@@ -460,7 +460,7 @@ class Assets
         }
 
         $key = md5($asset);
-        if (is_string($asset) && !array_key_exists($key, $this->inline_js)) {
+        if ($asset && is_string($asset) && !array_key_exists($key, $this->inline_js)) {
             $this->inline_js[$key] = $data;
         }