diff --git a/addons/mass_mailing/static/src/scss/mass_mailing_mobile_preview.scss b/addons/mass_mailing/static/src/scss/mass_mailing_mobile_preview.scss
index 675da25c00b..d50d3dfc502 100644
--- a/addons/mass_mailing/static/src/scss/mass_mailing_mobile_preview.scss
+++ b/addons/mass_mailing/static/src/scss/mass_mailing_mobile_preview.scss
@@ -18,7 +18,7 @@
                 font-family: $o-we-font-family;
 
                 .btn-close {
-                    filter: invert(1) grayscale(100%) brightness(200%);
+                    filter: invert(50%) grayscale(100%) brightness(200%);
                 }
 
                 h4 {