diff --git a/web/templates/admin/certification.html b/web/templates/admin/certification.html
index 5c8c7dc..fd1b3a4 100644
--- a/web/templates/admin/certification.html
+++ b/web/templates/admin/certification.html
@@ -187,10 +187,24 @@
 <script>
     window.addEventListener("DOMContentLoaded", (event) => {
         document.querySelectorAll("select.common-reasons").forEach(elem => {
-            let textarea = elem.parentNode.parentNode.getElementsByTagName("textarea")[0];
+            let textarea = elem.parentNode.parentNode.getElementsByTagName("textarea")[0],
+                approveButton = elem.parentNode.parentNode.parentNode.parentNode.querySelector("button.is-success");
+
+            // Grey out the Approve button if a rejection reason is filled out.
+            let setApproveState = () => {
+                if (textarea.value.length > 0) {
+                    approveButton.disabled = "disabled";
+                } else {
+                    approveButton.disabled = null;
+                }
+            };
+
+            textarea.addEventListener("change", setApproveState);
+            textarea.addEventListener("keyup", setApproveState);
             elem.addEventListener("change", (e) => {
                 textarea.value = elem.value;
-            })
+                setApproveState();
+            });
         })
     });
 </script>