less/input.less

@@ -119,7 +119,7 @@
         opacity: 1;
       }
 
-      &:disabled {
+      &:disabled, &.uk-disabled {
         background: transparent;
         color: var(--input-color-disabled);
         -webkit-text-fill-color: var(--input-color-disabled);

less/utility.less

@@ -7,6 +7,10 @@
 
 .hook-utility-misc() {
   /* Border */
+  .uk-border-box {
+    box-sizing: border-box;
+  }
+
   .uk-border {
     border: @border-width solid @border-color;
   }