diff --git a/github-dark.css b/github-dark.css
index e85fb4770..0715dfeba 100644
--- a/github-dark.css
+++ b/github-dark.css
@@ -8508,6 +8508,9 @@
   .blob-code, .blob-code-inner {
     color: var(--ghd-code-color, #ccc) !important;
   }
+  .cm-tab {
+    overflow: hidden !important;
+  }
 }
 @-moz-document regexp("^https://www\.zuora\.com.*github\.com.*$") {
   /* Styles the payment form iframe */
diff --git a/tools/build-usercss.js b/tools/build-usercss.js
index 6c23669a8..81e12d5b4 100644
--- a/tools/build-usercss.js
+++ b/tools/build-usercss.js
@@ -73,6 +73,9 @@ function makeTabs(css) {
   pre, .highlight, .diff-table, .tab-size {
     tab-size: ${tab} !important;
     -moz-tab-size: ${tab} !important;
+  }
+  .cm-tab {
+    width: ${tab}ch !important;
   } EOT;`);
   });
   return css.replace("  {{tab-sizes}}", tabs.join("\n"));