diff --git a/include/dblayer/functions_mysql.inc.php b/include/dblayer/functions_mysql.inc.php
index 6a173686d..d9a2ef2a7 100644
--- a/include/dblayer/functions_mysql.inc.php
+++ b/include/dblayer/functions_mysql.inc.php
@@ -503,7 +503,7 @@ INSERT INTO '.$table_name.'
         $is_first = false;
       }
       
-      if ($value === '')
+      if ($value === '' || is_null($value))
       {
         $query .= 'NULL';
       }
diff --git a/include/dblayer/functions_mysqli.inc.php b/include/dblayer/functions_mysqli.inc.php
index 21adbeabe..4b28678a0 100644
--- a/include/dblayer/functions_mysqli.inc.php
+++ b/include/dblayer/functions_mysqli.inc.php
@@ -594,7 +594,7 @@ INSERT INTO '.$table_name.'
         $is_first = false;
       }
       
-      if ($value === '')
+      if ($value === '' || is_null($value))
       {
         $query .= 'NULL';
       }