diff --git a/README.md b/README.md
index 3ec627a5..333a3930 100644
--- a/README.md
+++ b/README.md
@@ -49,10 +49,11 @@ Building Instructions
 
 Parchment is only designed for building in Linux and may not work in other OSes. You'll need to install Git and Node version >= 16.
 
-The upstream projects are included as git submodules. Start by initializing the submodules:
+The upstream projects are included as Git submodules. Start by cloning the Git repository:
 
 ```
-git submodule update --init --recursive
+git clone --recurse-submodules https://github.com/curiousdannii/parchment.git
+cd parchment
 ```
 
 Then install the `npm` dependencies:
diff --git a/package.json b/package.json
index a74dca46..3af56e38 100644
--- a/package.json
+++ b/package.json
@@ -15,6 +15,7 @@
   "type": "module",
   "dependencies": {
     "base32768": "^3.0.1",
+    "body-scroll-lock": "^4.0.0-beta.0",
     "emglken": "^0.6.0",
     "fflate": "^0.8.1",
     "file-saver": "^2.0.5",
@@ -25,6 +26,7 @@
     "pretty-bytes": "^6.1.1"
   },
   "devDependencies": {
+    "@types/body-scroll-lock": "^3.1.2",
     "@types/file-saver": "^2.0.7",
     "@types/jquery": "^3.5.11",
     "@types/js-cookie": "^3.0.4",
diff --git a/src/upstream/asyncglk b/src/upstream/asyncglk
index dcb9d7f9..08c28406 160000
--- a/src/upstream/asyncglk
+++ b/src/upstream/asyncglk
@@ -1 +1 @@
-Subproject commit dcb9d7f93b8d77e28909aeddcaccc8e4b9b91afc
+Subproject commit 08c284061a72f1f74f4dfa5e8ccb79f79661ee59
diff --git a/src/web/parchment.css b/src/web/parchment.css
index 18927616..a7885c9c 100644
--- a/src/web/parchment.css
+++ b/src/web/parchment.css
@@ -9,6 +9,11 @@ https://github.com/curiousdannii/parchment
 
 */
 
+body, html {
+  height: 100%;
+  width: 100%;
+}
+
 body {
   background: var(--glkote-page-bg);
   color: var(--glkote-buffer-fg);