diff --git a/package.json b/package.json
index 9f3f254..8a1c0ff 100644
--- a/package.json
+++ b/package.json
@@ -58,6 +58,7 @@
     "glob": "^7.1.6",
     "listr": "^0.14.3",
     "lodash.keyby": "^4.6.0",
-    "mime-types": "^2.1.25"
+    "mime-types": "^2.1.25",
+    "slash": "^3.0.0"
   }
 }
diff --git a/src/s3.ts b/src/s3.ts
index ab70bc4..09bf218 100644
--- a/src/s3.ts
+++ b/src/s3.ts
@@ -1,6 +1,7 @@
 import glob from 'glob'
 import { promisify } from 'util'
 import { join, relative } from 'path'
+import slash from 'slash'
 import Listr, { ListrTask } from 'listr'
 import { S3 } from 'aws-sdk'
 import { createReadStream, lstatSync } from 'fs'
@@ -12,7 +13,8 @@ import { getContentType } from './utils/mime'
 const globAsync = promisify(glob)
 
 const resolveObjectKey = (cwd: string, base: string, filename: string) => {
-  return relative(join(cwd, base), filename)
+  const p = relative(join(cwd, base), filename)
+  return slash(p)
 }
 
 type FileDef = { name: string; key: string; md5: string }
diff --git a/yarn.lock b/yarn.lock
index 5c3eeba..71759d4 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3863,6 +3863,11 @@ slash@^2.0.0:
   resolved "https://registry.yarnpkg.com/slash/-/slash-2.0.0.tgz#de552851a1759df3a8f206535442f5ec4ddeab44"
   integrity sha512-ZYKh3Wh2z1PpEXWr0MpSBZ0V6mZHAQfYevttO11c51CaWjGTaadiKZ+wVt1PbMlDV5qhMFslpZCemhwOK7C89A==
 
+slash@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/slash/-/slash-3.0.0.tgz#6539be870c165adbd5240220dbe361f1bc4d4634"
+  integrity sha512-g9Q1haeby36OSStwb4ntCGGGaKsaVSjQ68fBxoQcutl5fS1vuY18H3wSt3jFyFtrkx+Kz0V1G85A4MyAdDMi2Q==
+
 slice-ansi@0.0.4:
   version "0.0.4"
   resolved "https://registry.yarnpkg.com/slice-ansi/-/slice-ansi-0.0.4.tgz#edbf8903f66f7ce2f8eafd6ceed65e264c831b35"