diff -u b/inline_entity_form.module b/inline_entity_form.module
--- b/inline_entity_form.module
+++ b/inline_entity_form.module
@@ -1387,7 +1387,26 @@
         $data = check_plain($data);
 
         if (isset($field['process']) && function_exists($field['process'])) {
-          $data = call_user_func($field['process'], $data);
+          if (isset($field['arguments']) && is_array($field['arguments'])) {
+            // swap integer 1 for the data, similair to hook_menu
+            $arguments = array();
+            $replaced = false;
+            foreach ($field['arguments'] as $arg) {
+              if ($arg === 1) {
+                $arguments[] = $data;
+                $replaced = true;
+              } else {
+                $arguments[] = $arg;
+              }
+            }
+            // If the data was never swapped in, use it as the first argument
+            if (!$replaced) {
+              array_unshift($arguments, $data);
+            }
+          } else {
+            $arguments = array($data);
+          }
+          $data = call_user_func_array($field['process'], $arguments);
         }
       }
       elseif ($field['type'] == 'field') {