diff --git a/subsys/portability/cmsis_rtos_v2/event_flags.c b/subsys/portability/cmsis_rtos_v2/event_flags.c
index 7e48e16..a9eb3df 100644
--- a/subsys/portability/cmsis_rtos_v2/event_flags.c
+++ b/subsys/portability/cmsis_rtos_v2/event_flags.c
@@ -57,13 +57,16 @@
 uint32_t osEventFlagsSet(osEventFlagsId_t ef_id, uint32_t flags)
 {
 	struct cmsis_rtos_event_cb *events = (struct cmsis_rtos_event_cb *)ef_id;
+	uint32_t rv;
+
 	if ((ef_id == NULL) || (flags & osFlagsError)) {
 		return osFlagsErrorParameter;
 	}
 
-	k_event_post(&events->z_event, flags);
+	rv = k_event_test(&events->z_event, 0xFFFFFFFF);
+	k_event_post(&events->z_event, flags & ~rv);
 
-	return k_event_test(&events->z_event, 0xFFFFFFFF);
+	return flags & ~rv;
 }
 
 /**