diff --git a/CHANGELOG.md b/CHANGELOG.md
index 36964cae541..adc8dd4ac4e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
 
 - Fixed `EuiErrorBoundary` error message not showing in non-Chromium browsers ([#4324](https://github.com/elastic/eui/pull/4324))
 - Fixed `EuiToolTip` closing during initial positioning period ([#4327](https://github.com/elastic/eui/pull/4327))
+- Added `!default` to SASS variables of `EuiCollapsibleNav` ([#4335](https://github.com/elastic/eui/pull/4335))
 
 **Theme: Amsterdam**
 
diff --git a/src/components/collapsible_nav/_variables.scss b/src/components/collapsible_nav/_variables.scss
index f883cd5f8a2..fbb573d7d2b 100644
--- a/src/components/collapsible_nav/_variables.scss
+++ b/src/components/collapsible_nav/_variables.scss
@@ -1,14 +1,14 @@
 // Sizing
-$euiCollapsibleNavWidth: $euiSize * 20; // ~ 320px
+$euiCollapsibleNavWidth: $euiSize * 20 !default; // ~ 320px
 
-$euiCollapsibleNavGroupLightBackgroundColor: $euiPageBackgroundColor;
+$euiCollapsibleNavGroupLightBackgroundColor: $euiPageBackgroundColor !default;
 
 $euiCollapsibleNavGroupDarkBackgroundColor: lightOrDarkTheme(
   shade($euiColorDarkestShade, 20%),
   shade($euiColorLightestShade, 50%),
-);
+) !default;
 
 $euiCollapsibleNavGroupDarkHighContrastColor: makeGraphicContrastColor(
   $euiColorPrimary,
   $euiCollapsibleNavGroupDarkBackgroundColor
-);
+) !default;