diff --git a/logback-classic-blackbox/src/test/java/ch/qos/logback/classic/blackbox/net/SMTPAppender_GreenTest.java b/logback-classic-blackbox/src/test/java/ch/qos/logback/classic/blackbox/net/SMTPAppender_GreenTest.java
index b270f4840d..741945c056 100644
--- a/logback-classic-blackbox/src/test/java/ch/qos/logback/classic/blackbox/net/SMTPAppender_GreenTest.java
+++ b/logback-classic-blackbox/src/test/java/ch/qos/logback/classic/blackbox/net/SMTPAppender_GreenTest.java
@@ -169,8 +169,9 @@ void waitUntilEmailIsSent() throws InterruptedException {
         es.shutdown();
         boolean terminated = es.awaitTermination(TIMEOUT, TimeUnit.MILLISECONDS);
         // this assertion may be needlessly strict, skipped on MacOS
+        System.getProperty("os.name");
         if(!terminated && !EnvUtil.isMacOs()) {
-            fail("executor elapsed before accorded delay");
+            fail("executor elapsed before accorded delay " + System.getProperty("os.name"));
         }
 
     }