diff --git a/.changeset/twelve-comics-enjoy.md b/.changeset/twelve-comics-enjoy.md
new file mode 100644
index 000000000000..6322bcfd6aa9
--- /dev/null
+++ b/.changeset/twelve-comics-enjoy.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Force Vite to use HTTP/1 in dev mode, so `dev --https` works again
diff --git a/packages/kit/src/core/dev/index.js b/packages/kit/src/core/dev/index.js
index 3bcd1a9b1b54..a1e9a948e20b 100644
--- a/packages/kit/src/core/dev/index.js
+++ b/packages/kit/src/core/dev/index.js
@@ -85,6 +85,14 @@ export async function dev({ cwd, port, host, https, config }) {
 		merged_config.server.https = https;
 	}
 
+	// by default, when enabling HTTPS in Vite, it also enables HTTP/2
+	// however, node-fetch's Request implementation does not like the HTTP/2 headers
+	// we set a no-op proxy config to force Vite to downgrade to TLS-only
+	// see https://vitejs.dev/config/#server-https
+	if (merged_config.server.https && !merged_config.server.proxy) {
+		merged_config.server.proxy = {};
+	}
+
 	if (port) {
 		merged_config.server.port = port;
 	}