diff --git a/Examples/SwiftSerialIM/Sources/main.swift b/Examples/SwiftSerialIM/Sources/main.swift
index 8606309..e81ceeb 100644
--- a/Examples/SwiftSerialIM/Sources/main.swift
+++ b/Examples/SwiftSerialIM/Sources/main.swift
@@ -95,6 +95,7 @@ do {
         observer in
 
         backgroundRead()
+        return nil
     }
 
     pthread_create(&readingThread, nil, pthreadFunc, nil)