diff --git a/packages/remix-dev/cli/migrate/migrations/replace-remix-imports/getTransformOptions.ts b/packages/remix-dev/cli/migrate/migrations/replace-remix-imports/getTransformOptions.ts
index d36b774e825..ed64b108bec 100644
--- a/packages/remix-dev/cli/migrate/migrations/replace-remix-imports/getTransformOptions.ts
+++ b/packages/remix-dev/cli/migrate/migrations/replace-remix-imports/getTransformOptions.ts
@@ -14,9 +14,12 @@ const resolveRuntime = async ({
   scripts,
 }: PackageJson): Promise<Runtime> => {
   // match `remix setup <runtime>` in `postinstall` script
-  let remixSetupMatch = scripts?.postinstall?.match(/remix setup (\w+)/);
+  let remixSetupMatch = scripts?.postinstall?.match(/remix setup(\s+\w+)/);
   if (remixSetupMatch && remixSetupMatch.length >= 2) {
-    let postinstallRuntime = remixSetupMatch[1];
+    // `remix setup` defaults to `node
+    if (remixSetupMatch[1] === undefined) return "node";
+
+    let postinstallRuntime = remixSetupMatch[1].trim();
     if (isRuntime(postinstallRuntime)) {
       return postinstallRuntime;
     }
diff --git a/packages/remix-dev/cli/migrate/migrations/replace-remix-imports/index.ts b/packages/remix-dev/cli/migrate/migrations/replace-remix-imports/index.ts
index d66f0c46437..145903b97d7 100644
--- a/packages/remix-dev/cli/migrate/migrations/replace-remix-imports/index.ts
+++ b/packages/remix-dev/cli/migrate/migrations/replace-remix-imports/index.ts
@@ -78,9 +78,10 @@ function* getTasks({
   }
 
   // `remix setup` in `postinstall`
-  let remixSetup = packageJson.scripts?.postinstall?.match(/remix setup \w+/);
+  let remixSetup =
+    packageJson.scripts?.postinstall?.match(/remix setup(\s+\w+)?/);
   if (remixSetup) {
-    yield `Remove \`${remixSetup}\` from your \`postinstall\` script`;
+    yield `Remove \`${remixSetup[0]}\` from your \`postinstall\` script`;
   }
 }