diff --git a/dist/index.js b/dist/index.js
index 4479318..b63b5fd 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -1363,7 +1363,7 @@ class GitHubHelper {
                     };
                 })));
                 core.info(`Creating tree for local commit ${commit.sha}`);
-                const { data: tree } = yield this.octokit.rest.git.createTree(Object.assign(Object.assign({}, repository), { base_tree: parentCommit.sha, tree: treeObjects }));
+                const { data: tree } = yield this.octokit.rest.git.createTree(Object.assign(Object.assign({}, repository), { base_tree: parentCommit.tree, tree: treeObjects }));
                 treeSha = tree.sha;
                 core.info(`Created tree ${treeSha} for local commit ${commit.sha}`);
             }
diff --git a/src/github-helper.ts b/src/github-helper.ts
index 209a709..08aede0 100644
--- a/src/github-helper.ts
+++ b/src/github-helper.ts
@@ -286,7 +286,7 @@ export class GitHubHelper {
       core.info(`Creating tree for local commit ${commit.sha}`)
       const {data: tree} = await this.octokit.rest.git.createTree({
         ...repository,
-        base_tree: parentCommit.sha, // but this should probably be tree
+        base_tree: parentCommit.tree,
         tree: treeObjects
       })
       treeSha = tree.sha