diff --git a/fillpdf.module b/fillpdf.module
index 428ba0130a938e835ce5d3bceb54380d8cf58ef0..2348ce5dc194a364042cf680cadccdf842315fce 100644
--- a/fillpdf.module
+++ b/fillpdf.module
@@ -525,7 +525,7 @@ function fillpdf_context_to_link($fid, $context, $sample = FALSE) {
  *   Array of IDs of entities from which to draw data. IDs may be integers or
  *   strings depending on the entity type.
  *
- * @return object
+ * @return object|null
  *   When $handle is FALSE, this function returns the variable it would have
  *   used to invoke hook_fillpdf_merge_pre_handle(). When $handle is TRUE, it
  *   returns nothing.
@@ -1075,6 +1075,9 @@ function _fillpdf_build_options_object($force_download, $flatten, $fillpdf_info,
  *   to the user's browser.
  *
  *   Here, specifically, it's for generating the filename of the handled PDF.
+ *
+ * @return null
+ *   Normally, this calls drupal_exit(). In error conditions, it returns NULL.
  */
 function fillpdf_merge_perform_pdf_action($fillpdf_object, $action = 'download', $force_download = FALSE) {
   $pdf_info = $fillpdf_object->info;