diff --git a/boards/sim/sim/sim/configs/citest/defconfig b/boards/sim/sim/sim/configs/citest/defconfig
index 8d38d4171c4..70ffa16a74e 100644
--- a/boards/sim/sim/sim/configs/citest/defconfig
+++ b/boards/sim/sim/sim/configs/citest/defconfig
@@ -87,6 +87,7 @@ CONFIG_TESTING_FSTEST=y
 CONFIG_TESTING_FSTEST_MOUNTPT="/tmp"
 CONFIG_TESTING_GETPRIME=y
 CONFIG_TESTING_MM=y
+CONFIG_TESTING_OPEN_MEMSTREAM=y
 CONFIG_TESTING_OSTEST=y
 CONFIG_TESTING_SCANFTEST=y
 CONFIG_TESTING_SCANFTEST_FNAME="/tmp/test.txt"
diff --git a/tools/ci/testrun/script/test_os/test_os.py b/tools/ci/testrun/script/test_os/test_os.py
index ef026d22745..bd8c6f39386 100644
--- a/tools/ci/testrun/script/test_os/test_os.py
+++ b/tools/ci/testrun/script/test_os/test_os.py
@@ -46,6 +46,8 @@ def test_stdio(p):
     assert ret == 0
     ret = p.sendCommand("fmemopen_test", "FAILED: 0")
     assert ret == 0
+    ret = p.sendCommand("open_memstream_test", "FAILED: 0")
+    assert ret == 0
 
 
 @pytest.mark.run(order=-2)