diff --git a/docs/resources/changelog.md b/docs/resources/changelog.md
index efebde46c..636bb38e3 100644
--- a/docs/resources/changelog.md
+++ b/docs/resources/changelog.md
@@ -20,6 +20,7 @@ The docs have been updated to use the new `custom-elements.json` file. If you're
 - Added `sl-request-close` event to `sl-dialog` and `sl-drawer`
 - Added `dialog.denyClose` and `drawer.denyClose` animations
 - Fixed a bug in `sl-color-picker` where setting `value` immediately wouldn't trigger an update
+- Fixed a bug in `sl-dialog` and `sl-drawer` where setting `open` intially didn't set a focus trap
 - Fixed a bug that resulted in form controls having incorrect validity when `disabled` was initially set [#473](https://github.com/shoelace-style/shoelace/issues/473)
 - Fixed a bug in the docs that caused the metadata file to be requested twice
 - Updated the docs to use the new `custom-elements.json` for component metadata
diff --git a/src/components/dialog/dialog.ts b/src/components/dialog/dialog.ts
index 5014ea000..0e78b9bab 100644
--- a/src/components/dialog/dialog.ts
+++ b/src/components/dialog/dialog.ts
@@ -95,6 +95,11 @@ export default class SlDialog extends LitElement {
 
   firstUpdated() {
     this.dialog.hidden = !this.open;
+
+    if (this.open) {
+      this.modal.activate();
+      lockBodyScrolling(this);
+    }
   }
 
   disconnectedCallback() {
diff --git a/src/components/drawer/drawer.ts b/src/components/drawer/drawer.ts
index 5677ad926..33fe6d709 100644
--- a/src/components/drawer/drawer.ts
+++ b/src/components/drawer/drawer.ts
@@ -112,6 +112,11 @@ export default class SlDrawer extends LitElement {
 
   firstUpdated() {
     this.drawer.hidden = !this.open;
+
+    if (this.open && !this.contained) {
+      this.modal.activate();
+      lockBodyScrolling(this);
+    }
   }
 
   disconnectedCallback() {