diff --git a/src/app/modules/angular-slickgrid/styles/slick-default-theme.scss b/src/app/modules/angular-slickgrid/styles/slick-default-theme.scss
index 1c542e24e..9dfc3d828 100644
--- a/src/app/modules/angular-slickgrid/styles/slick-default-theme.scss
+++ b/src/app/modules/angular-slickgrid/styles/slick-default-theme.scss
@@ -14,6 +14,7 @@
    .slick-header-column {
      background: $grid-header-background;
      // background-color: #EBECEE;
+     box-sizing: content-box !important; /* this here only for Firefox! */
    }
 
    .slick-header-columns {
diff --git a/src/app/modules/angular-slickgrid/styles/slick-grid.scss b/src/app/modules/angular-slickgrid/styles/slick-grid.scss
index 2a1601949..af3db161f 100644
--- a/src/app/modules/angular-slickgrid/styles/slick-grid.scss
+++ b/src/app/modules/angular-slickgrid/styles/slick-grid.scss
@@ -28,6 +28,7 @@
   .slick-group-header-column.ui-state-default {
     position: relative;
     display: inline-block;
+    box-sizing: content-box !important; /* this here only for Firefox! */
     overflow: hidden;
     -o-text-overflow: ellipsis;
     text-overflow: ellipsis;