diff --git a/src/data_utils.inc.php b/src/data_utils.inc.php
index a28a514..c494dad 100644
--- a/src/data_utils.inc.php
+++ b/src/data_utils.inc.php
@@ -182,3 +182,13 @@ function val_enum($enum, $val, $check_enum_validity = true)
   return $val;
 }
 
+function val_blob($val)
+{
+  if(is_null($val))
+    return $val;
+
+  if(!is_string($val))
+    throw new Exception("Bad item, not a blob string(" . serialize($val) . ")");
+
+  return $val;
+}