diff --git a/scst/README b/scst/README
index dcc60a67e..fe90af02e 100644
--- a/scst/README
+++ b/scst/README
@@ -398,6 +398,16 @@ Module scst supports the following parameters:
    to be consumed by all SCSI commands of a device at any given time. By
    default, it is approximately 2/5 of scst_max_cmd_mem.
 
+ - auto_cm_assignment - enables the copy managers auto registration.
+   If a device is not registered in the copy manager, it can not be
+   source or target of EXTENDED COPY commands. Enabled by default.
+   Disable, if you want to manually control the copy manager
+   registration or need to change a device, e.g. a DM cache device, with
+   SCST LUN on top of it to avoid extra reference the copy manager holds
+   on this device. In the later case you can also remove this reference
+   by manually deleting the corresponding copy manager LUN via sysfs interface
+   (/sys/kernel/scst_tgt/targets/copy_manager/copy_manager_tgt/luns/mgmt).
+
 
 SCST sysfs interface
 --------------------
diff --git a/scst/README_in-tree b/scst/README_in-tree
index 0b0731710..494c5a8b0 100644
--- a/scst/README_in-tree
+++ b/scst/README_in-tree
@@ -268,6 +268,16 @@ Module scst supports the following parameters:
    consumed by the SCST commands for data buffers at any given time. By
    default it is approximately TotalMem/4.
 
+ - auto_cm_assignment - enables the copy managers auto registration.
+   If a device is not registered in the copy manager, it can not be
+   source or target of EXTENDED COPY commands. Enabled by default.
+   Disable, if you want to manually control the copy manager
+   registration or need to change a device, e.g. a DM cache device, with
+   SCST LUN on top of it to avoid extra reference the copy manager holds
+   on this device. In the later case you can also remove this reference
+   by manually deleting the corresponding copy manager LUN via sysfs interface
+   (/sys/kernel/scst_tgt/targets/copy_manager/copy_manager_tgt/luns/mgmt).
+
 
 SCST sysfs interface
 --------------------
diff --git a/scst/src/scst_copy_mgr.c b/scst/src/scst_copy_mgr.c
index 4310c4ed1..d7206f43d 100644
--- a/scst/src/scst_copy_mgr.c
+++ b/scst/src/scst_copy_mgr.c
@@ -2709,7 +2709,7 @@ int scst_cm_on_dev_register(struct scst_device *dev)
 	scst_assert_activity_suspended();
 	lockdep_assert_held(&scst_mutex);
 
-	if (!dev->handler->auto_cm_assignment_possible)
+	if (!scst_auto_cm_assignment || !dev->handler->auto_cm_assignment_possible)
 		goto out;
 
 	res = scst_cm_dev_register(dev, SCST_MAX_LUN);
diff --git a/scst/src/scst_main.c b/scst/src/scst_main.c
index 8d672b79b..1440bc4b1 100644
--- a/scst/src/scst_main.c
+++ b/scst/src/scst_main.c
@@ -175,6 +175,7 @@ cpumask_t default_cpu_mask;
 static unsigned int scst_max_cmd_mem;
 unsigned int scst_max_dev_cmd_mem;
 int scst_forcibly_close_sessions;
+int scst_auto_cm_assignment = true;
 
 module_param_named(scst_threads, scst_threads, int, S_IRUGO);
 MODULE_PARM_DESC(scst_threads, "SCSI target threads count");
@@ -193,6 +194,9 @@ MODULE_PARM_DESC(forcibly_close_sessions,
 "If enabled, close the sessions associated with an access control group (ACG)"
 " when an ACG is deleted via sysfs instead of returning -EBUSY");
 
+module_param_named(auto_cm_assignment, scst_auto_cm_assignment, int,
+		   S_IWUSR | S_IRUGO);
+MODULE_PARM_DESC(auto_cm_assignment, "Enables the copy managers auto registration");
 
 struct scst_dev_type scst_null_devtype = {
 	.name = "none",
diff --git a/scst/src/scst_priv.h b/scst/src/scst_priv.h
index 12698cbce..c3cb2fb33 100644
--- a/scst/src/scst_priv.h
+++ b/scst/src/scst_priv.h
@@ -151,6 +151,7 @@ extern int scst_threads;
 extern unsigned int scst_max_dev_cmd_mem;
 
 extern int scst_forcibly_close_sessions;
+extern int scst_auto_cm_assignment;
 
 extern mempool_t *scst_mgmt_mempool;
 extern mempool_t *scst_mgmt_stub_mempool;