diff --git a/library-css/modal.scss b/library-css/modal.scss
index 1ad8c55..3500567 100644
--- a/library-css/modal.scss
+++ b/library-css/modal.scss
@@ -15,6 +15,14 @@
   transition: transform linear .3s, opacity linear .3s;
 }
 
+.fs-modal .fs-modal-bg {
+  position: fixed;
+  top: 0;
+  right: 0;
+  bottom: 0;
+  left: 0;
+}
+
 .fs-modal .fs-modal-dialog {
   background-color: white;
   border-radius: 4px;