diff --git a/gatsby-node.js b/gatsby-node.js
index e98bbf7..b31bdb1 100644
--- a/gatsby-node.js
+++ b/gatsby-node.js
@@ -59,7 +59,7 @@ exports.sourceNodes = async ({ actions, createNodeId, createContentDigest }, opt
 
   for (const _path of paths) {
     let githubPath = path.join(root, _path.replace(process.cwd(), ''))
-    if (githubPath.charAt(0) === '/') githubPath = githubPath.substr(1)
+    if (githubPath.charAt(0) === path.sep) githubPath = githubPath.substr(1)
 
     let contributors = []
     if (token) {
diff --git a/test/gatsby-node.test.js b/test/gatsby-node.test.js
index e593374..a14eff8 100644
--- a/test/gatsby-node.test.js
+++ b/test/gatsby-node.test.js
@@ -10,6 +10,7 @@
  * governing permissions and limitations under the License.
  */
 
+const path = require('path')
 const mockGithubFetchContributors = jest.fn()
 const mockGithubFetch = jest.fn()
 jest.mock('../src/gql', () => ({
@@ -108,14 +109,16 @@ describe('gatsby-node', () => {
       .mockResolvedValueOnce(contributors[1])
 
     const root = 'my-root'
-    options.root = `/${root}` // coverage
-    await expect(gatsbyNode.sourceNodes(gatsbyHelpers, options)).resolves.toEqual(undefined)
+    const _options = Object.assign({}, options)
+    _options.root = `/${root}` // coverage
+    await expect(gatsbyNode.sourceNodes(gatsbyHelpers, _options)).resolves.toEqual(undefined)
     expect(gatsbyHelpers.actions.createNode).toHaveBeenCalledTimes(pages.length + 1)
     expect(mockGithubFetchContributors).toHaveBeenCalledTimes(pages.length)
 
     pages.forEach((page, index) => {
-      const { owner, name, branch, token } = options.repo
-      expect(mockGithubFetchContributors).toHaveBeenNthCalledWith(index + 1, owner, name, branch, `${root}/${page}`, token)
+      const { owner, name, branch, token } = _options.repo
+      const pagePath = path.join(root, page)
+      expect(mockGithubFetchContributors).toHaveBeenNthCalledWith(index + 1, owner, name, branch, pagePath, token)
       // skip the very first createNode, which is a Github object
       expect(gatsbyHelpers.actions.createNode).toHaveBeenNthCalledWith(index + 2, expect.objectContaining({
         contributors: contributors[index],