diff --git a/src/get-app-authentication.ts b/src/get-app-authentication.ts
index 519ae318..f5e15945 100644
--- a/src/get-app-authentication.ts
+++ b/src/get-app-authentication.ts
@@ -7,7 +7,7 @@ export async function getAppAuthentication({
   privateKey,
   timeDifference,
 }: State & {
-  timeDifference?: number;
+  timeDifference?: number | undefined;
 }): Promise<AppAuthentication> {
   try {
     const appAuthentication = timeDifference
diff --git a/src/get-installation-authentication.ts b/src/get-installation-authentication.ts
index 686bcdda..9a471fa0 100644
--- a/src/get-installation-authentication.ts
+++ b/src/get-installation-authentication.ts
@@ -40,6 +40,7 @@ export async function getInstallationAuthentication(
       state.cache,
       optionsWithInstallationTokenFromState,
     );
+
     if (result) {
       const {
         token,
@@ -52,7 +53,7 @@ export async function getInstallationAuthentication(
         repositorySelection,
       } = result;
 
-      const authParams = {
+      return toTokenAuthentication({
         installationId,
         token,
         createdAt,
@@ -61,15 +62,8 @@ export async function getInstallationAuthentication(
         repositorySelection,
         repositoryIds,
         repositoryNames,
-      };
-
-      if (singleFileName) {
-        Object.assign(authParams, {
-          singleFileName,
-        });
-      }
-
-      return toTokenAuthentication(authParams);
+        singleFileName,
+      });
     }
   }
 
diff --git a/src/types.ts b/src/types.ts
index 67d54d13..830804ae 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -164,7 +164,7 @@ export type InstallationAccessTokenData = {
   repositorySelection: REPOSITORY_SELECTION;
   repositoryIds: number[] | undefined;
   repositoryNames: string[] | undefined;
-  singleFileName?: string;
+  singleFileName?: string | undefined;
 };
 
 export type CacheData = InstallationAccessTokenData;