diff --git a/lib/filestorage/file_storage.php b/lib/filestorage/file_storage.php
index 21779e8233b..05d015787a8 100644
--- a/lib/filestorage/file_storage.php
+++ b/lib/filestorage/file_storage.php
@@ -987,6 +987,12 @@ class file_storage {
      * @return stored_file instance
      */
     public function convert_image($file_record, $fid, $newwidth = NULL, $newheight = NULL, $keepaspectratio = true, $quality = NULL) {
+        if (!function_exists('imagecreatefromstring')) {
+            //Most likely the GD php extension isn't installed
+            //image conversion cannot succeed
+            throw new file_exception('storedfileproblem', 'imagecreatefromstring() doesnt exist. The PHP extension "GD" must be installed for image conversion.');
+        }
+
         if ($fid instanceof stored_file) {
             $fid = $fid->get_id();
         }
diff --git a/mod/data/field/picture/field.class.php b/mod/data/field/picture/field.class.php
index 3086c845504..269e916815f 100644
--- a/mod/data/field/picture/field.class.php
+++ b/mod/data/field/picture/field.class.php
@@ -266,6 +266,7 @@ class data_field_picture extends data_field_base {
             $fs->convert_image($file_record, $file, $this->field->param4, $this->field->param5, true);
             return true;
         } catch (Exception $e) {
+            debugging($e->getMessage());
             return false;
         }
     }