diff --git a/build/cli.cjs b/build/cli.cjs
index 2a9b043bf9..b4916110d8 100755
--- a/build/cli.cjs
+++ b/build/cli.cjs
@@ -304,7 +304,7 @@ function readScript() {
     }
     if (ext === ".md") {
       script = transformMarkdown(script);
-      tempPath = getFilepath(dir, base);
+      tempPath = getFilepath(dir, base, EXT);
     }
     if (argSlice) (0, import_index.updateArgv)(argv._.slice(argSlice));
     return { script, scriptPath, tempPath };
diff --git a/src/cli.ts b/src/cli.ts
index 5b8783c7a0..cf28081493 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -232,7 +232,7 @@ async function readScript() {
   }
   if (ext === '.md') {
     script = transformMarkdown(script)
-    tempPath = getFilepath(dir, base)
+    tempPath = getFilepath(dir, base, EXT)
   }
   if (argSlice) updateArgv(argv._.slice(argSlice))
 
diff --git a/test/cli.test.js b/test/cli.test.js
index 936325d115..fabc7a6beb 100644
--- a/test/cli.test.js
+++ b/test/cli.test.js
@@ -347,6 +347,12 @@ console.log(a);
     assert.ok(p.stdout.includes('Hello, world!'))
   })
 
+  test('markdown scripts from stdin with --ext .md', async () => {
+    const md = '# Test\n\n```js\necho("md-stdin-ok")\n```\n'
+    const p = await $`node build/cli.js --ext='.md' <<< ${md}`
+    assert.match(p.stdout, /md-stdin-ok/)
+  })
+
   test('exceptions are caught', async () => {
     const out1 = await $`node build/cli.js <<<${'await $`wtf`'}`.nothrow()
     const out2 = await $`node build/cli.js <<<'throw 42'`.nothrow()