diff --git a/extension/src/service-worker/__tests__/git-host.test.ts b/extension/src/service-worker/__tests__/git-host.test.ts
index f177cfa..5aae457 100644
--- a/extension/src/service-worker/__tests__/git-host.test.ts
+++ b/extension/src/service-worker/__tests__/git-host.test.ts
@@ -55,6 +55,7 @@ describe('GitHubHost.putBlob', () => {
     expect(fetchMock).toHaveBeenCalledTimes(6);
     expect(fetchMock.mock.calls[0][0]).toContain('/git/blobs');
     expect(fetchMock.mock.calls[1][0]).toContain('/git/refs/heads/');
+    expect(fetchMock.mock.calls[2][0]).toContain('/git/commits/');
     expect(fetchMock.mock.calls[3][0]).toContain('/git/trees');
     expect(fetchMock.mock.calls[4][0]).toContain('/git/commits');
     expect(fetchMock.mock.calls[5][1]?.method).toBe('PATCH');
diff --git a/extension/src/service-worker/github.ts b/extension/src/service-worker/github.ts
index c3f2748..0ee250c 100644
--- a/extension/src/service-worker/github.ts
+++ b/extension/src/service-worker/github.ts
@@ -135,14 +135,16 @@ export class GitHubHost implements GitHost {
     // 2. Get current ref (branch tip commit SHA).
     const refResp = await fetch(`${this.gitApiBase}/refs/heads/${this.branch}`, { headers: this.headers });
     if (!refResp.ok) {
-      throw new Error(`GitHub putBlob get-ref ${this.branch}: ${refResp.status} ${refResp.statusText}`);
+      const text = await refResp.text();
+      throw new Error(`GitHub putBlob get-ref ${this.branch}: ${refResp.status} ${text}`);
     }
     const { object: { sha: commitSha } } = await refResp.json() as { object: { sha: string } };
 
     // 3. Get current commit's tree SHA.
     const commitResp = await fetch(`${this.gitApiBase}/commits/${commitSha}`, { headers: this.headers });
     if (!commitResp.ok) {
-      throw new Error(`GitHub putBlob get-commit ${commitSha}: ${commitResp.status} ${commitResp.statusText}`);
+      const text = await commitResp.text();
+      throw new Error(`GitHub putBlob get-commit ${commitSha}: ${commitResp.status} ${text}`);
     }
     const { tree: { sha: baseTreeSha } } = await commitResp.json() as { tree: { sha: string } };