Toaster appears briefly with black background before switching to default color.

[dasilvas3]

This is only happening in IE-11
When the toaster is triggered from a controller, it briefly appears with black background and then it displays with correct default color.

I tried to set the CSS class toaster-info as following
.toast-info {
background-color: #2f96b4!important;
}
but no avail.
Cheers