diff --git a/TESTS/mbedmicro-rtos-mbed/systimer/main.cpp b/TESTS/mbedmicro-rtos-mbed/systimer/main.cpp
index 4f688799ba..e1e474d6d4 100644
--- a/TESTS/mbedmicro-rtos-mbed/systimer/main.cpp
+++ b/TESTS/mbedmicro-rtos-mbed/systimer/main.cpp
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if !MBED_TICKLESS
+#ifndef MBED_TICKLESS
 #error [NOT_SUPPORTED] Tickless mode not supported for this target.
 #endif