diff --git a/ts/deck-options/BUILD.bazel b/ts/deck-options/BUILD.bazel
index d2c589472..d1f7bc0f1 100644
--- a/ts/deck-options/BUILD.bazel
+++ b/ts/deck-options/BUILD.bazel
@@ -50,6 +50,7 @@ ts_library(
         "lib",
         "//ts/components",
         "//ts/lib",
+        "//ts/sveltelib",
         "@npm//@popperjs",
         "@npm//svelte2tsx",
     ],
diff --git a/ts/deck-options/index.ts b/ts/deck-options/index.ts
index 3d6794f89..27b5a2b47 100644
--- a/ts/deck-options/index.ts
+++ b/ts/deck-options/index.ts
@@ -5,6 +5,7 @@
 @typescript-eslint/no-explicit-any: "off",
  */
 
+import "sveltelib/cross-unit";
 import { getDeckOptionsInfo, DeckOptionsState } from "./lib";
 import { setupI18n, ModuleName } from "lib/i18n";
 import { checkNightMode } from "lib/nightmode";
diff --git a/ts/editor/index.ts b/ts/editor/index.ts
index 57671daac..9daeb9a23 100644
--- a/ts/editor/index.ts
+++ b/ts/editor/index.ts
@@ -6,6 +6,8 @@
 @typescript-eslint/no-explicit-any: "off",
  */
 
+import "sveltelib/cross-unit";
+
 import { filterHTML } from "html-filter";
 import { updateActiveButtons } from "./toolbar";
 import { setupI18n, ModuleName } from "lib/i18n";
diff --git a/ts/sveltelib/cross-unit.ts b/ts/sveltelib/cross-unit.ts
new file mode 100644
index 000000000..c83b80520
--- /dev/null
+++ b/ts/sveltelib/cross-unit.ts
@@ -0,0 +1,6 @@
+// Copyright: Ankitects Pty Ltd and contributors
+// License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
+
+// allow Svelte add-ons
+import * as svelte_internal from "svelte/internal";
+window["svelte_internal"] = svelte_internal;