diff --git a/packages/babel-plugin-proposal-decorators/src/transformer-legacy.js b/packages/babel-plugin-proposal-decorators/src/transformer-legacy.js
index 0eb0ebdbd87a..53cfe47df91d 100644
--- a/packages/babel-plugin-proposal-decorators/src/transformer-legacy.js
+++ b/packages/babel-plugin-proposal-decorators/src/transformer-legacy.js
@@ -237,7 +237,7 @@ export default {
 
     const replacement = decoratedClassToExpression(decl);
     if (replacement) {
-      path.replaceWithMultiple([
+      const [varDeclPath] = path.replaceWithMultiple([
         replacement,
         t.exportNamedDeclaration(null, [
           t.exportSpecifier(
@@ -246,6 +246,10 @@ export default {
           ),
         ]),
       ]);
+
+      if (!decl.node.id) {
+        path.scope.registerDeclaration(varDeclPath);
+      }
     }
   },
   ClassDeclaration(path) {
diff --git a/packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/input.mjs b/packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/input.mjs
new file mode 100644
index 000000000000..90ba5e106f57
--- /dev/null
+++ b/packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/input.mjs
@@ -0,0 +1,4 @@
+function myDecorator(decoratee) {}
+
+@myDecorator
+export default class {}
diff --git a/packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/options.json b/packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/options.json
new file mode 100644
index 000000000000..51aa897d2c31
--- /dev/null
+++ b/packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/options.json
@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    "transform-typescript",
+    [ "proposal-decorators", { "legacy": true } ]
+  ]
+}
diff --git a/packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/output.mjs b/packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/output.mjs
new file mode 100644
index 000000000000..5e99551db44a
--- /dev/null
+++ b/packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/output.mjs
@@ -0,0 +1,7 @@
+var _class2;
+
+function myDecorator(decoratee) {}
+
+let _class = myDecorator(_class2 = class {}) || _class2;
+
+export { _class as default };