diff --git a/cli/dev/register.ts b/cli/dev/register.ts
index 7fa0f1b..723dbb2 100644
--- a/cli/dev/register.ts
+++ b/cli/dev/register.ts
@@ -38,6 +38,10 @@ export const registerDev = (program: Command) => {
 
       if (file) {
         absolutePath = path.resolve(file)
+        if (!absolutePath.endsWith(".tsx")) {
+          console.error("Error: Only .tsx files are supported")
+          return
+        }
       } else {
         const entrypointPath = path.resolve("index.tsx")
         if (fs.existsSync(entrypointPath)) {
diff --git a/package.json b/package.json
index 3298310..0fddf89 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "@tscircuit/cli",
   "main": "dist/main.js",
   "type": "module",
-  "version": "0.1.19",
+  "version": "0.1.20",
   "bin": {
     "tsci": "./dist/main.js"
   },