diff --git a/src/binary-encoding.adoc b/src/binary-encoding.adoc
index a620840..27ad59a 100644
--- a/src/binary-encoding.adoc
+++ b/src/binary-encoding.adoc
@@ -59,6 +59,7 @@ error codes.
 |  SBI_ERR_BAD_RANGE         | -11   | Bad (or invalid) range
 |  SBI_ERR_TIMEOUT           | -12   | Failed due to timeout
 |  SBI_ERR_IO                | -13   | Input/Output error
+|  SBI_ERR_DENIED_LOCKED     | -14   | Denied or not allowed due to lock status
 |===
 
 An `ECALL` with an unsupported SBI extension ID (*EID*) or an unsupported SBI
diff --git a/src/ext-firmware-features.adoc b/src/ext-firmware-features.adoc
index ecfa033..1241c89 100644
--- a/src/ext-firmware-features.adoc
+++ b/src/ext-firmware-features.adoc
@@ -116,6 +116,9 @@ firmware feature to be set according to the `value` and `flags` parameters for
 which per feature supported values are described in
 <<table_fw_features_attribute_values>> and flags in <<table_fw_features_flags>>.
 
+NOTE: The set operation will succeed if requested `value` matches the existing
+value.
+
 [#table_fw_features_flags]
 .FWFT Firmware Features Set Flags
 [cols="1,1,3", width=90%, align="center", options="header"]
@@ -143,9 +146,10 @@ returned in `sbiret.error` are shown in <<table_fw_features_set_errors>> below.
 | SBI_ERR_INVALID_PARAM | Provided `value` or `flags` parameter is invalid.
 | SBI_ERR_DENIED        | `feature` set operation failed because either: +
                           - it was denied by the SBI implementation +
-                          - `feature` is locked +
                           - `feature` is reserved or is platform-specific and
                           unimplemented
+| SBI_ERR_DENIED_LOCKED | `feature` set operation failed because the `feature`
+			  is locked
 | SBI_ERR_FAILED        | The set operation failed for unspecified or unknown
                           other reasons.
 |===