diff --git a/res/css/_common.scss b/res/css/_common.scss
index 16d3f29726..87fa4578b1 100644
--- a/res/css/_common.scss
+++ b/res/css/_common.scss
@@ -303,7 +303,7 @@ input[type=text]:focus, input[type=password]:focus, textarea:focus {
 }
 
 .mx_Dialog_lightbox .mx_Dialog_background {
-    opacity: 0.85;
+    opacity: $lightbox-background-bg-opacity;
     background-color: $lightbox-background-bg-color;
 }
 
diff --git a/res/themes/dark/css/_dark.scss b/res/themes/dark/css/_dark.scss
index cf1fd17e58..bd7057c3e4 100644
--- a/res/themes/dark/css/_dark.scss
+++ b/res/themes/dark/css/_dark.scss
@@ -85,6 +85,7 @@ $dialog-close-fg-color: #9fa9ba;
 
 $dialog-background-bg-color: $header-panel-bg-color;
 $lightbox-background-bg-color: #000;
+$lightbox-background-bg-opacity: 85%;
 
 $settings-grey-fg-color: #a2a2a2;
 $settings-profile-placeholder-bg-color: #21262c;
@@ -242,7 +243,7 @@ $composer-shadow-color: rgba(0, 0, 0, 0.28);
 @define-mixin mx_DialogButton_secondary {
     // flip colours for the secondary ones
     font-weight: 600;
-    border: 1px solid $accent-color ! important;
+    border: 1px solid $accent-color !important;
     color: $accent-color;
     background-color: $button-secondary-bg-color;
 }
diff --git a/res/themes/legacy-dark/css/_legacy-dark.scss b/res/themes/legacy-dark/css/_legacy-dark.scss
index ff58314bdd..9b2365a621 100644
--- a/res/themes/legacy-dark/css/_legacy-dark.scss
+++ b/res/themes/legacy-dark/css/_legacy-dark.scss
@@ -83,6 +83,7 @@ $dialog-close-fg-color: #9fa9ba;
 
 $dialog-background-bg-color: $header-panel-bg-color;
 $lightbox-background-bg-color: #000;
+$lightbox-background-bg-opacity: 85%;
 
 $settings-grey-fg-color: #a2a2a2;
 $settings-profile-placeholder-bg-color: #e7e7e7;
diff --git a/res/themes/legacy-light/css/_legacy-light.scss b/res/themes/legacy-light/css/_legacy-light.scss
index 121366decb..7cb7082c4e 100644
--- a/res/themes/legacy-light/css/_legacy-light.scss
+++ b/res/themes/legacy-light/css/_legacy-light.scss
@@ -127,6 +127,7 @@ $dialog-close-fg-color: #c1c1c1;
 
 $dialog-background-bg-color: #e9e9e9;
 $lightbox-background-bg-color: #000;
+$lightbox-background-bg-opacity: 95%;
 
 $imagebody-giflabel: rgba(0, 0, 0, 0.7);
 $imagebody-giflabel-border: rgba(0, 0, 0, 0.2);
diff --git a/res/themes/light/css/_light.scss b/res/themes/light/css/_light.scss
index f082247754..dc26c4d652 100644
--- a/res/themes/light/css/_light.scss
+++ b/res/themes/light/css/_light.scss
@@ -118,6 +118,7 @@ $dialog-close-fg-color: #c1c1c1;
 
 $dialog-background-bg-color: #e9e9e9;
 $lightbox-background-bg-color: #000;
+$lightbox-background-bg-opacity: 95%;
 
 $imagebody-giflabel: rgba(0, 0, 0, 0.7);
 $imagebody-giflabel-border: rgba(0, 0, 0, 0.2);