diff --git a/ui/css/cloudstack3.css b/ui/css/cloudstack3.css
index a4571dbfe9f..e3ecf6c7466 100644
--- a/ui/css/cloudstack3.css
+++ b/ui/css/cloudstack3.css
@@ -4890,6 +4890,10 @@ label.error {
   text-shadow: 0px 1px 1px #FFFFFF;
 }
 
+.multi-wizard.instance-wizard .data-disk-offering .content .section.custom-size {
+  position: relative;
+}
+
 .multi-wizard.instance-wizard .data-disk-offering .content .section.custom-size input[type=radio] {
   float: left;
 }
@@ -4900,6 +4904,13 @@ label.error {
   margin: 6px -1px 0 8px;
 }
 
+.multi-wizard.instance-wizard .data-disk-offering .content .section.custom-size label.error {
+  position: absolute;
+  top: 29px;
+  left: 242px;
+  font-size: 10px;
+}
+
 /*** Network*/
 .multi-wizard.instance-wizard .no-network {
   background: #FFFFFF;
diff --git a/ui/index.jsp b/ui/index.jsp
index ee01286a5a9..5fcc02c08b3 100644
--- a/ui/index.jsp
+++ b/ui/index.jsp
@@ -173,7 +173,7 @@
                   <div class="slider custom-size"></div>
                   <label class="size">100 GB</label>
 
-                  <input type="text" name="size" value="1" />
+                  <input type="text" class="required digits" name="size" value="1" />
                   <label class="size">GB</label>
                 </div>
               </div>