diff --git a/packages/styles/scss/components/masthead/_masthead-l1.scss b/packages/styles/scss/components/masthead/_masthead-l1.scss
index 7c78b32a51a..42fddd239c3 100644
--- a/packages/styles/scss/components/masthead/_masthead-l1.scss
+++ b/packages/styles/scss/components/masthead/_masthead-l1.scss
@@ -26,7 +26,12 @@ $search-transition-timing: 95ms;
     transition-timing-function: $search-transition;
     overflow: visible;
 
-    @include carbon--breakpoint-down(800px) {
+    // Exclude the target breakpoint itself (800px) by subtracting .02.
+    // This has been addressed in Carbon core, but only for breakpoint
+    // keywords, i.e. 'md', 'lg'.
+    // The calculation is not applied to numeric values.
+    // https://github.com/carbon-design-system/carbon/blob/master/packages/layout/scss/_breakpoint.scss#L172
+    @include carbon--breakpoint-down(799.98px) {
       display: none;
     }