diff --git a/test-suite/tests/r6rs-ports.test b/test-suite/tests/r6rs-ports.test
index 829258f87..df12e5cbc 100644
--- a/test-suite/tests/r6rs-ports.test
+++ b/test-suite/tests/r6rs-ports.test
@@ -342,6 +342,7 @@
                                                     close!)))
 
       (close-port port)
+      (gc) ; Test for marking a closed port.
       closed?)))