diff --git a/proto/attributes/attributes.proto b/proto/attributes/attributes.proto
index 6cdeb6b96f..3d58a8d116 100644
--- a/proto/attributes/attributes.proto
+++ b/proto/attributes/attributes.proto
@@ -32,7 +32,7 @@ message AttributeDefinition {
   repeated AttributeDefinitionValue values = 4;
 
   //optional attribute group by filtering rules
-  repeated AttributeDefinitionValue group_by = 9;
+  AttributeDefinitionValue group_by = 9;
 }
 
 // Reference to an attribute value, one of descriptor or embedded value
diff --git a/sdk/attributes/attributes.pb.go b/sdk/attributes/attributes.pb.go
index 8f865a9451..bcba418686 100644
--- a/sdk/attributes/attributes.pb.go
+++ b/sdk/attributes/attributes.pb.go
@@ -145,7 +145,7 @@ type AttributeDefinition struct {
 	// possible values
 	Values []*AttributeDefinitionValue `protobuf:"bytes,4,rep,name=values,proto3" json:"values,omitempty"`
 	// optional attribute group by filtering rules
-	GroupBy []*AttributeDefinitionValue `protobuf:"bytes,9,rep,name=group_by,json=groupBy,proto3" json:"group_by,omitempty"`
+	GroupBy *AttributeDefinitionValue `protobuf:"bytes,9,opt,name=group_by,json=groupBy,proto3" json:"group_by,omitempty"`
 }
 
 func (x *AttributeDefinition) Reset() {
@@ -208,7 +208,7 @@ func (x *AttributeDefinition) GetValues() []*AttributeDefinitionValue {
 	return nil
 }
 
-func (x *AttributeDefinition) GetGroupBy() []*AttributeDefinitionValue {
+func (x *AttributeDefinition) GetGroupBy() *AttributeDefinitionValue {
 	if x != nil {
 		return x.GroupBy
 	}
@@ -1453,7 +1453,7 @@ var file_attributes_attributes_proto_rawDesc = []byte{
 	0x61, 0x74, 0x74, 0x72, 0x69, 0x62, 0x75, 0x74, 0x65, 0x73, 0x2e, 0x41, 0x74, 0x74, 0x72, 0x69,
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