diff --git a/index.d.ts b/index.d.ts
index 90f6263..c0a81a6 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -63,7 +63,7 @@ interface IDockerComposePushOptions extends IDockerComposeOptions {
 }
 
 interface IDockerComposeResult {
-    exitCode: ?number;
+    exitCode?: number;
     out: string;
     err: string;
 }