diff --git a/src/librustdoc/html/static/rustdoc.css b/src/librustdoc/html/static/rustdoc.css
index d091cc0c0965..0ab130009ca0 100644
--- a/src/librustdoc/html/static/rustdoc.css
+++ b/src/librustdoc/html/static/rustdoc.css
@@ -182,6 +182,18 @@ nav.sub {
 	top: 0;
 	bottom: 0;
 	overflow: auto;
+	/* Improve the sidebar display on firefox */
+	scrollbar-width: thin;
+}
+
+/* Improve the sidebar display on webkit-based browsers */
+.sidebar::-webkit-scrollbar {
+	width: 8px;
+}
+
+/* Improve the sidebar display on webkit-based browsers */
+.sidebar::-webkit-scrollbar-track {
+	-webkit-box-shadow: inset 0;
 }
 
 .sidebar .block > ul > li {
diff --git a/src/librustdoc/html/static/themes/dark.css b/src/librustdoc/html/static/themes/dark.css
index ff32a0fa09e4..155492e8a6a7 100644
--- a/src/librustdoc/html/static/themes/dark.css
+++ b/src/librustdoc/html/static/themes/dark.css
@@ -30,6 +30,18 @@ pre {
 
 .sidebar {
 	background-color: #505050;
+	/* Improve the sidebar display on firefox */
+	scrollbar-color: rgba(32,34,37,.6) transparent;
+}
+
+/* Improve the sidebar display on webkit-based browsers */
+.sidebar::-webkit-scrollbar-track {
+	background-color: #717171;
+}
+
+/* Improve the sidebar display on webkit-based browsers */
+.sidebar::-webkit-scrollbar-thumb {
+	background-color: rgba(32, 34, 37, .6);
 }
 
 .sidebar .current {
diff --git a/src/librustdoc/html/static/themes/light.css b/src/librustdoc/html/static/themes/light.css
index 2b2819f7126b..488c34a61fb9 100644
--- a/src/librustdoc/html/static/themes/light.css
+++ b/src/librustdoc/html/static/themes/light.css
@@ -32,6 +32,18 @@ pre {
 
 .sidebar {
 	background-color: #F1F1F1;
+	/* Improve the sidebar display on firefox */
+	scrollbar-color: rgba(36, 37, 39, 0.6) #d9d9d9;
+}
+
+/* Improve the sidebar display on webkit-based browsers */
+.sidebar::-webkit-scrollbar-track {
+	background-color: #dcdcdc;
+}
+
+/* Improve the sidebar display on webkit-based browsers */
+.sidebar::-webkit-scrollbar-thumb {
+	background-color: rgba(36, 37, 39, 0.6);
 }
 
 .sidebar .current {