diff --git a/grade/tests/behat/grade_aggregation.feature b/grade/tests/behat/grade_aggregation.feature
index 68a91041234..ce5cb455584 100644
--- a/grade/tests/behat/grade_aggregation.feature
+++ b/grade/tests/behat/grade_aggregation.feature
@@ -421,6 +421,8 @@ Feature: We can use calculated grade totals
       | Extra credit  | 0   |
       | Maximum grade | 200 |
       | Rescale existing grades | No |
+    # Change window size to ultra-wide to avoid 'out-of-bounds' random failures.
+    And I change window size to "5120x2160"
     And I give the grade "21.00" to the user "Student 1" for the grade item "Manual item 2"
     And I press "Save changes"
     And I give the grade "20.00" to the user "Student 1" for the grade item "Manual item 2"
@@ -432,6 +434,8 @@ Feature: We can use calculated grade totals
       | Extra credit  | 0   |
       | Maximum grade | 100 |
       | Rescale existing grades | No |
+    # Change window size to ultra-wide to avoid 'out-of-bounds' random failures.
+    And I change window size to "5120x2160"
     And I give the grade "21.00" to the user "Student 1" for the grade item "Manual item 2"
     And I press "Save changes"
     And I give the grade "20.00" to the user "Student 1" for the grade item "Manual item 2"