diff --git a/packages/mermaid/src/themes/theme-dark.js b/packages/mermaid/src/themes/theme-dark.js
index 8fde494bd..b0bc6ff5b 100644
--- a/packages/mermaid/src/themes/theme-dark.js
+++ b/packages/mermaid/src/themes/theme-dark.js
@@ -64,6 +64,7 @@ class Theme {
     this.sectionBkgColor = darken('#EAE8D9', 30);
     this.altSectionBkgColor = 'calculated';
     this.sectionBkgColor2 = '#EAE8D9';
+    this.excludeBkgColor = darken(this.sectionBkgColor, 10);
     this.taskBorderColor = rgba(255, 255, 255, 70);
     this.taskBkgColor = 'calculated';
     this.taskTextColor = 'calculated';