diff --git a/static/lille/_custom.scss b/static/lille/_custom.scss
index e08335eb..242b0ec1 100644
--- a/static/lille/_custom.scss
+++ b/static/lille/_custom.scss
@@ -138,6 +138,9 @@ div.gru-nav .gru-nav-button {
 		margin-bottom: 0;
 		position: absolute;
 		width: $width;
+		@media screen and ($max-mobile-viewport) {
+			width: 100%;
+		}
 		border-top: 0;
 		z-index: 1000;
 	}