diff --git a/apps/theming/lib/Themes/DarkHighContrastTheme.php b/apps/theming/lib/Themes/DarkHighContrastTheme.php
index f219c3b3e8743..9e13470e6ad7d 100644
--- a/apps/theming/lib/Themes/DarkHighContrastTheme.php
+++ b/apps/theming/lib/Themes/DarkHighContrastTheme.php
@@ -101,6 +101,12 @@ public function getCustomCss(): string {
 			.menutoggle {
 				opacity: 1 !important;
 			}
+			#app-navigation {
+				border-right: 1px solid var(--color-border);
+			}
+			div.crumb {
+				filter: brightness(150%);
+			}
 		";
 	}
 }
diff --git a/apps/theming/lib/Themes/HighContrastTheme.php b/apps/theming/lib/Themes/HighContrastTheme.php
index fda02058446ce..421e703321459 100644
--- a/apps/theming/lib/Themes/HighContrastTheme.php
+++ b/apps/theming/lib/Themes/HighContrastTheme.php
@@ -101,6 +101,9 @@ public function getCustomCss(): string {
 			.menutoggle {
 				opacity: 1 !important;
 			}
+			#app-navigation {
+				border-right: 1px solid var(--color-border);
+			}
 		";
 	}
 }