diff --git a/jsr.json b/jsr.json
index f3936ad..c8aa643 100644
--- a/jsr.json
+++ b/jsr.json
@@ -1,6 +1,6 @@
 {
   "name": "@nostr/tools",
-  "version": "2.23.11",
+  "version": "2.23.12",
   "exports": {
     ".": "./index.ts",
     "./core": "./core.ts",
diff --git a/nipb0.ts b/nipb0.ts
index 4b86ffc..ad5c72c 100644
--- a/nipb0.ts
+++ b/nipb0.ts
@@ -393,7 +393,10 @@ export async function uploadBlob(server: string, blob: Blob | File, opts?: Uploa
   const url = new URL('/upload', server).toString()
   const sha256 = await computeBlobSha256(blob)
 
-  const headers: Record<string, string> = { 'X-SHA-256': sha256 }
+  const headers: Record<string, string> = {
+    'X-SHA-256': sha256,
+    'Content-Type': getBlobType(blob) || 'application/octet-stream',
+  }
 
   if (opts?.auth) {
     const authEvent = typeof opts.auth === 'boolean' ? await opts.onAuth?.(server, sha256) : opts.auth
diff --git a/package.json b/package.json
index 746bbc3..fea6d20 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "type": "module",
   "name": "nostr-tools",
-  "version": "2.23.11",
+  "version": "2.23.12",
   "description": "Tools for making a Nostr client.",
   "repository": {
     "type": "git",