diff --git a/src/fs/lzma.d.ts b/src/fs/lzma.d.ts
index 3ff923935..1767b2067 100644
--- a/src/fs/lzma.d.ts
+++ b/src/fs/lzma.d.ts
@@ -1 +1 @@
-declare module "lzma/src/lzma-d-min";
+declare module "lzma/src/lzma-d";
diff --git a/src/fs/migration.ts b/src/fs/migration.ts
index 39f478e39..c09c7797f 100644
--- a/src/fs/migration.ts
+++ b/src/fs/migration.ts
@@ -5,6 +5,15 @@
  */
 import { toByteArray } from "base64-js";
 
+import lzma from "lzma/src/lzma-d";
+
+// LZMA isn't a proper module.
+// When bundled it assigns to window. At dev time it works via the above import.
+const LZMA =
+  typeof window !== "undefined" && (window as any).LZMA
+    ? (window as any).LZMA
+    : lzma.LZMA;
+
 // There are other fields that we don't use.
 export interface Migration {
   meta: {
@@ -34,10 +43,7 @@ export const parseMigrationFromUrl = (
   try {
     if (urlPart) {
       const bytes = toByteArray(urlPart);
-      const json = JSON.parse(
-        // FIXME, reinstate decompression with a working module.
-        /*LZMA.decompress(*/ new TextDecoder().decode(bytes) /*)*/
-      );
+      const json = JSON.parse(LZMA.decompress(bytes));
       if (isMigration(json)) {
         let postMigrationUrl = parts[0];
         // This was previously stripped off by the versioner but for now do it ourselves: