diff --git a/app/assets/javascripts/discourse/app/components/d-modal.hbs b/app/assets/javascripts/discourse/app/components/d-modal.hbs
index c98c0d928be..5c50992aca8 100644
--- a/app/assets/javascripts/discourse/app/components/d-modal.hbs
+++ b/app/assets/javascripts/discourse/app/components/d-modal.hbs
@@ -76,7 +76,7 @@
             </div>
           {{/if}}
 
-          <div class="modal-body" tabindex="-1">
+          <div class={{concat-class "modal-body" @bodyClass}} tabindex="-1">
             {{#if (has-block "body")}}
               {{yield to="body"}}
             {{else}}
diff --git a/app/assets/javascripts/discourse/tests/integration/components/d-modal-test.js b/app/assets/javascripts/discourse/tests/integration/components/d-modal-test.js
index fa41c66eff9..fd84f89d2e3 100644
--- a/app/assets/javascripts/discourse/tests/integration/components/d-modal-test.js
+++ b/app/assets/javascripts/discourse/tests/integration/components/d-modal-test.js
@@ -72,4 +72,13 @@ module("Integration | Component | d-modal", function (hooks) {
 
     closeModalCalled = false;
   });
+
+  test("header and body classes", async function (assert) {
+    await render(
+      hbs`<DModal @inline={{true}} @bodyClass="my-body-class" @headerClass="my-header-class" @title="Hello world" />`
+    );
+
+    assert.dom(".d-modal .modal-header").hasClass("my-header-class");
+    assert.dom(".d-modal .modal-body").hasClass("my-body-class");
+  });
 });