diff --git a/attribute.go b/attribute.go
index 69610f9..412a430 100644
--- a/attribute.go
+++ b/attribute.go
@@ -303,7 +303,54 @@ func (e *AttributeEncoder) Encode(attribute string, value interface{}) error {
 			}
 		}
 	default:
-		return fmt.Errorf("type %T is not supported", value)
+		if tag != TagBeginCollection {
+			return fmt.Errorf("type %T is not supported", value)
+		}
+
+		if err := e.encodeTag(TagBeginCollection); err != nil {
+			return err
+		}
+
+		if err := e.encodeString(attribute); err != nil {
+			return err
+		}
+
+		if err := e.writeNullByte(); err != nil {
+			return err
+		}
+
+		for member, value := range value.(map[string]interface{}) {
+			if err := e.encodeTag(TagMemberName); err != nil {
+				return err
+			}
+			if err := e.writeNullByte(); err != nil {
+				return err
+			}
+			if err := e.encodeString(member); err != nil {
+				return err
+			}
+			if err := e.encodeTag(TagKeyword); err != nil {
+				return err
+			}
+			if err := e.writeNullByte(); err != nil {
+				return err
+			}
+			if err := e.encodeString(value.(string)); err != nil {
+				return err
+			}
+		}
+
+		if err := e.encodeTag(TagEndCollection); err != nil {
+			return err
+		}
+
+		if err := e.writeNullByte(); err != nil {
+			return err
+		}
+
+		if err := e.writeNullByte(); err != nil {
+			return err
+		}
 	}
 
 	return nil
diff --git a/constants.go b/constants.go
index 31c8b29..e6e1a02 100644
--- a/constants.go
+++ b/constants.go
@@ -353,6 +353,7 @@ const (
 	AttributeNumberOfDocuments      = "number-of-documents"
 	AttributeJobOriginatingUserName = "job-originating-user-name"
 	AttributeOutputOrder            = "outputorder"
+	AttributeMediaCol               = "media-col"
 )
 
 // Default attributes
@@ -416,5 +417,6 @@ var (
 		AttributeStatusMessage:          TagText,
 		AttributeLimit:                  TagInteger,
 		AttributeOutputOrder:            TagName,
+		AttributeMediaCol:               TagBeginCollection,
 	}
 )