diff --git a/src/commitSha.ts b/src/commitSha.ts
index 2d6b2985..8db28b31 100644
--- a/src/commitSha.ts
+++ b/src/commitSha.ts
@@ -429,7 +429,7 @@ export const getSHAForPullRequestEvent = async (
 
   if (
     !github.context.payload.pull_request?.base?.ref ||
-    github.context.payload.head?.repo?.fork === 'true'
+    github.context.payload.pull_request?.head?.repo?.fork === true
   ) {
     diff = '..'
   }
diff --git a/src/utils.ts b/src/utils.ts
index f1672d70..d550b332 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -908,7 +908,7 @@ export const canDiffCommits = async ({
   } else {
     const {exitCode, stderr} = await exec.getExecOutput(
       'git',
-      ['diff', '--quiet', sha1, sha2],
+      ['diff', '--no-patch', sha1, sha2],
       {
         cwd,
         ignoreReturnCode: true,