diff --git a/core/src/main/java/hudson/Launcher.java b/core/src/main/java/hudson/Launcher.java
index c6e39a27d3e8..d0fcd7b6c107 100644
--- a/core/src/main/java/hudson/Launcher.java
+++ b/core/src/main/java/hudson/Launcher.java
@@ -761,6 +761,7 @@ protected final void printCommandLine(@Nonnull String[] cmd, @CheckForNull FileP
                 buf.append(c);
         }
         listener.getLogger().println(buf.toString());
+        listener.getLogger().flush();
     }
 
     /**
diff --git a/test/src/test/java/hudson/util/ArgumentListBuilder2Test.java b/test/src/test/java/hudson/util/ArgumentListBuilder2Test.java
index 3ba9183fff19..fe8c19f6f76b 100644
--- a/test/src/test/java/hudson/util/ArgumentListBuilder2Test.java
+++ b/test/src/test/java/hudson/util/ArgumentListBuilder2Test.java
@@ -27,7 +27,6 @@
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
 import static org.junit.Assume.*;
 import hudson.Functions;
 import hudson.Launcher.LocalLauncher;
@@ -46,7 +45,6 @@
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.StringWriter;
-import java.net.URL;
 
 /**
  * @author Kohsuke Kawaguchi
@@ -71,8 +69,7 @@ public void slaveMask() throws Exception {
 
         StringWriter out = new StringWriter();
         assertEquals(0,s.createLauncher(new StreamTaskListener(out)).launch().cmds(args).join());
-        System.out.println(out);
-        assertTrue(out.toString().contains("$ java ********"));
+        assertThat(out.toString(), containsString("$ java ********"));
     }
 
     @Test