diff --git a/casadm/extended_err_msg.c b/casadm/extended_err_msg.c
index a7e6a7d..9d3b4fe 100644
--- a/casadm/extended_err_msg.c
+++ b/casadm/extended_err_msg.c
@@ -53,6 +53,10 @@ struct {
 		OCF_ERR_CACHE_NOT_EXIST,
 		"Cache ID does not exist"
 	},
+	{
+		OCF_ERR_CORE_NOT_EXIST,
+		"Core ID does not exist"
+	},
 	{
 		OCF_ERR_CACHE_EXIST,
 		"Cache ID already exists"
diff --git a/modules/cas_cache/layer_cache_management.c b/modules/cas_cache/layer_cache_management.c
index 2b8b695..df9b486 100644
--- a/modules/cas_cache/layer_cache_management.c
+++ b/modules/cas_cache/layer_cache_management.c
@@ -916,7 +916,7 @@ int cache_mngt_remove_core_from_cache(struct kcas_remove_core *cmd)
 
 	wait_for_completion_interruptible(&context.compl);
 
-	if (!result && cmd->detach) {
+	if (!result && !cmd->detach) {
 		cache_priv = ocf_cache_get_priv(cache);
 		mark_core_id_free(cache_priv->core_id_bitmap, cmd->core_id);
 	}