diff --git a/grade/report/grader/styles.php b/grade/report/grader/styles.php
index 14ab278fefa..524b8f7d5c4 100644
--- a/grade/report/grader/styles.php
+++ b/grade/report/grader/styles.php
@@ -4,6 +4,7 @@
 
 .gradestable th.user img {
     width: 20px;
+    height: 20px;
 }
 
 .gradestable th.user, .gradestable th.range {