diff --git a/.changeset/lucky-hairs-lie.md b/.changeset/lucky-hairs-lie.md
new file mode 100644
index 000000000..296f2206a
--- /dev/null
+++ b/.changeset/lucky-hairs-lie.md
@@ -0,0 +1,5 @@
+---
+'preact-cli': patch
+---
+
+Reverts automatic conversion of `--sw` flag in dev to a boolean, which stopped the debug service worker from attaching.
diff --git a/packages/cli/lib/commands/watch.js b/packages/cli/lib/commands/watch.js
index 0ccc6dcdd..f7c49f113 100644
--- a/packages/cli/lib/commands/watch.js
+++ b/packages/cli/lib/commands/watch.js
@@ -101,7 +101,9 @@ async function command(src, argv) {
 	}
 	argv.src = src || argv.src;
 	argv.production = false;
-	argv.sw = toBool(argv.sw);
+	if (argv.sw) {
+		argv.sw = toBool(argv.sw);
+	}
 
 	if (argv.https || process.env.HTTPS) {
 		let { key, cert, cacert } = argv;