diff --git a/desktop/src/main/stream.ts b/desktop/src/main/stream.ts
index d6768069f..12db786f5 100644
--- a/desktop/src/main/stream.ts
+++ b/desktop/src/main/stream.ts
@@ -44,33 +44,49 @@ export const registerStreamProtocol = () => {
         const path = decodeURIComponent(pathname);
         switch (host) {
             case "read":
-                try {
-                    return net.fetch(pathToFileURL(path).toString());
-                } catch (e) {
-                    log.error(`Failed to read stream for ${url}`, e);
-                    return new Response(`Failed to read stream: ${e.message}`, {
-                        status: 500,
-                    });
-                }
-
+                return handleRead(path);
             case "write":
-                try {
-                    await writeStream(path, request.body);
-                    return new Response("", { status: 200 });
-                } catch (e) {
-                    log.error(`Failed to write stream for ${url}`, e);
-                    return new Response(
-                        `Failed to write stream: ${e.message}`,
-                        { status: 500 },
-                    );
-                }
-
+                return handleWrite(path, request);
             default:
                 return new Response("", { status: 404 });
         }
     });
 };
 
+const handleRead = async (path: string) => {
+    try {
+        const res = await net.fetch(pathToFileURL(path).toString());
+        if (res.ok) {
+            // net.fetch defaults to text/plain, which might be fine
+            // in practice, but as an extra precaution indicate that
+            // this is binary data.
+            res.headers.set("Content-Type", "application/octet-stream");
+
+            // Add the file's size as the Content-Length header.
+            const fileSize = (await fs.stat(path)).size;
+            res.headers.set("Content-Length", `${fileSize}`);
+        }
+        return res;
+    } catch (e) {
+        log.error(`Failed to read stream at ${path}`, e);
+        return new Response(`Failed to read stream: ${e.message}`, {
+            status: 500,
+        });
+    }
+};
+
+const handleWrite = async (path: string, request: Request) => {
+    try {
+        await writeStream(path, request.body);
+        return new Response("", { status: 200 });
+    } catch (e) {
+        log.error(`Failed to write stream to ${path}`, e);
+        return new Response(`Failed to write stream: ${e.message}`, {
+            status: 500,
+        });
+    }
+};
+
 /**
  * Write a (web) ReadableStream to a file at the given {@link filePath}.
  *
diff --git a/web/apps/photos/src/utils/native-stream.ts b/web/apps/photos/src/utils/native-stream.ts
index 742c00a61..b98e6ae1a 100644
--- a/web/apps/photos/src/utils/native-stream.ts
+++ b/web/apps/photos/src/utils/native-stream.ts
@@ -17,6 +17,8 @@
  * @return A standard web {@link Response} object that contains the contents of
  * the file. In particular, `response.body` will be a {@link ReadableStream}
  * that can be used to read the files contents in a streaming, chunked, manner.
+ * Also, the response is guaranteed to have a "Content-Length" header indicating
+ * the size of the file that we'll be reading from disk.
  */
 export const readStream = async (path: string) => {
     const req = new Request(`stream://read${path}`, {