diff --git a/lib/grade/grade_item.php b/lib/grade/grade_item.php
index a67b112a446..62b752bd3c5 100644
--- a/lib/grade/grade_item.php
+++ b/lib/grade/grade_item.php
@@ -1221,6 +1221,13 @@ class grade_item extends grade_object {
             return false;
         }
 
+        // MDL-19407 If moving from a non-SWM category to a SWM category, convert aggregationcoef to 0
+        $currentparent = $this->load_parent_category();
+
+        if ($currentparent->aggregation != GRADE_AGGREGATE_WEIGHTED_MEAN2 && $parent_category->aggregation == GRADE_AGGREGATE_WEIGHTED_MEAN2) {
+            $this->aggregationcoef = 0;
+        }
+
         $this->force_regrading();
 
         // set new parent