diff --git a/object/service.proto b/object/service.proto
index 1d9f38d..28a8a17 100644
--- a/object/service.proto
+++ b/object/service.proto
@@ -551,7 +551,7 @@ message SearchV2Request {
     uint32 version = 2;
 
     // List of search expressions. Limited to 8. If additional attributes are
-    // requested (see attributes below) then the search expression MUST use
+    // requested (see attributes below) then the first filter's key MUST be
     // the first requested attribute. '$Object:containerID' and
     // '$Object:objectID' filters are prohibited.
     repeated SearchFilter filters = 3;
@@ -566,8 +566,9 @@ message SearchV2Request {
     // List of attribute names (including special ones as defined by
     // SearchFilter key) to include into the reply. Limited to 8, these
     // attributes also affect result ordering (result is ordered by attributes
-    // and then by OID). '$Object:containerID' and '$Object:objectID'
-    // attributes are prohibited.
+    // and then by OID). If additional attributes are requested, then the first
+    // filter's key (see filters above) MUST be the first requested attribute.
+    // '$Object:containerID' and '$Object:objectID' attributes are prohibited.
     repeated string attributes = 6;
   }
   // Body of search object request message.
diff --git a/proto-docs/object.md b/proto-docs/object.md
index 2134730..4782baf 100644
--- a/proto-docs/object.md
+++ b/proto-docs/object.md
@@ -834,10 +834,10 @@ Object Search request body
 | ----- | ---- | ----- | ----------- |
 | container_id | [neo.fs.v2.refs.ContainerID](#neo.fs.v2.refs.ContainerID) |  | Container where the search is being performed. |
 | version | [uint32](#uint32) |  | Version of the Query Language used. |
-| filters | [SearchFilter](#neo.fs.v2.object.SearchFilter) | repeated | List of search expressions. Limited to 8. If additional attributes are requested (see attributes below) then the search expression MUST use the first requested attribute. '$Object:containerID' and '$Object:objectID' filters are prohibited. |
+| filters | [SearchFilter](#neo.fs.v2.object.SearchFilter) | repeated | List of search expressions. Limited to 8. If additional attributes are requested (see attributes below) then the first filter's key MUST be the first requested attribute. '$Object:containerID' and '$Object:objectID' filters are prohibited. |
 | cursor | [string](#string) |  | Cursor to continue search. Can be omitted or empty for the new search. |
 | count | [uint32](#uint32) |  | Limits the number of responses to the specified number. Can't be more than 1000. |
-| attributes | [string](#string) | repeated | List of attribute names (including special ones as defined by SearchFilter key) to include into the reply. Limited to 8, these attributes also affect result ordering (result is ordered by attributes and then by OID). '$Object:containerID' and '$Object:objectID' attributes are prohibited. |
+| attributes | [string](#string) | repeated | List of attribute names (including special ones as defined by SearchFilter key) to include into the reply. Limited to 8, these attributes also affect result ordering (result is ordered by attributes and then by OID). If additional attributes are requested, then the first filter key (see filters above) MUST be the first requested attribute. '$Object:containerID' and '$Object:objectID' attributes are prohibited. |
 
 
 <a name="neo.fs.v2.object.SearchV2Response"></a>