diff --git a/paper-checkbox.html b/paper-checkbox.html
index fd20a69..6b677f3 100644
--- a/paper-checkbox.html
+++ b/paper-checkbox.html
@@ -70,6 +70,7 @@
         position: relative;
         width: 18px;
         height: 18px;
+        min-width: 18px;
         vertical-align: middle;
         background-color: var(--paper-checkbox-unchecked-background-color, transparent);
       }