Index: src/wp-admin/css/common.css
===================================================================
--- src/wp-admin/css/common.css	(revision 38209)
+++ src/wp-admin/css/common.css	(working copy)
@@ -1298,6 +1298,7 @@
 ------------------------------------------------------------------------------*/
 
 .notice,
+div[class="update-message"], /* back-compat for pre-4.6 */
 div.updated,
 div.error {
 	background: #fff;
@@ -1308,6 +1309,10 @@
 	padding: 1px 12px;
 }
 
+div[class="update-message"] { /* back-compat for pre-4.6 */
+	padding: 0.5em 12px;
+}
+
 .notice p,
 .notice-title,
 div.updated p,
@@ -1408,6 +1413,7 @@
 }
 
 .update-message p:before,
+div[class="update-message"]:before, /* back-compat for pre-4.6 */
 .updating-message p:before,
 .updated-message p:before,
 .import-php .updating-message:before,
@@ -1432,6 +1438,7 @@
 
 /* Update icon. */
 .update-message p:before,
+div[class="update-message"]:before, /* back-compat for pre-4.6 */
 .updating-message p:before,
 .import-php .updating-message:before,
 .button.updating-message:before,
@@ -1459,11 +1466,12 @@
 
 /* Error icon. */
 .update-message.notice-error p:before {
-	 color: #dc3232;
-	 content: "\f534";
+	color: #dc3232;
+	content: "\f534";
 }
 
 .wrap .notice p:before,
+div[class="update-message"]:before, /* back-compat for pre-4.6 */
 .import-php .updating-message:before {
 	margin-right: 6px;
 	vertical-align: bottom;
@@ -1552,7 +1560,8 @@
 	.wrap .notice p:before,
 	.button.installing:before,
 	.button.installed:before,
-	.update-message p:before {
+	.update-message p:before,
+	div[class="update-message"]:before { /* back-compat for pre-4.6 */
 		speak: none;
 	}
 }
Index: src/wp-admin/css/list-tables.css
===================================================================
--- src/wp-admin/css/list-tables.css	(revision 38209)
+++ src/wp-admin/css/list-tables.css	(working copy)
@@ -1350,10 +1350,18 @@
 	padding: 0;
 }
 
-.plugins .plugin-update-tr .notice {
+.plugins .plugin-update-tr .notice,
+.plugins .plugin-update-tr div[class="update-message"] { /* back-compat for pre-4.6 */
 	margin: 5px 20px 15px 40px;
 }
 
+.plugins .plugin-update-tr div[class="update-message"] { /* back-compat for pre-4.6 */
+	border-left-color: #ffb900;
+	background-color: #fff8e5;
+	-webkit-box-shadow: none;
+	box-shadow: none;
+}
+
 .plugins .notice p {
 	margin: 0.5em 0;
 }