diff --git a/src/functions/private.ts b/src/functions/private.ts
index 0c7bf46..6e8c955 100644
--- a/src/functions/private.ts
+++ b/src/functions/private.ts
@@ -92,14 +92,14 @@ namespace Functions.Private {
         ...context.repo,
         force: true,
         ref: refName,
-        sha: process.env.GITHUB_SHA,
+        sha: process.env.GITHUB_SHA!,
       }));
     } else {
       core.info(`Creating ref: refs/${refName} for: ${process.env.GITHUB_SHA}`);
       ({ data: upstreamRef } = await github.rest.git.createRef({
         ...context.repo,
         ref: `refs/${refName}`,
-        sha: process.env.GITHUB_SHA,
+        sha: process.env.GITHUB_SHA!,
       }));
     }
 
diff --git a/src/functions/public.ts b/src/functions/public.ts
index 01234e6..55c801b 100644
--- a/src/functions/public.ts
+++ b/src/functions/public.ts
@@ -79,7 +79,7 @@ namespace Functions {
    * @param {GitHub} github The octokit client instance
    */
   export async function findLatestRef(github: GitHub): Promise<LatestRef> {
-    let [majorLatest, majorSha] = [Functions.getPublishRefVersion(), process.env.GITHUB_SHA];
+    let [majorLatest, majorSha] = [Functions.getPublishRefVersion(), process.env.GITHUB_SHA!];
     let [repoLatest, repoSha] = [majorLatest, majorSha];
 
     const major = majorLatest.major;