diff --git a/roomserver/api/perform.go b/roomserver/api/perform.go
index 20931f807..249e6bdff 100644
--- a/roomserver/api/perform.go
+++ b/roomserver/api/perform.go
@@ -57,6 +57,11 @@ func (p *PerformError) JSONResponse() util.JSONResponse {
 			// TODO: Should we assert this is in fact JSON? E.g gjson parse?
 			JSON: json.RawMessage(p.Msg),
 		}
+	case PerformErrorNotFound:
+		return util.JSONResponse{
+			Code: http.StatusNotFound,
+			JSON: jsonerror.NotFound(p.Msg),
+		}
 	default:
 		return util.ErrorResponse(p)
 	}
@@ -73,6 +78,8 @@ const (
 	PerformErrorNoOperation PerformErrorCode = 4
 	// PerformErrRemote means that the request failed and the PerformError.Msg is the raw remote JSON error response
 	PerformErrRemote PerformErrorCode = 5
+	// PerformErrorNotFound means the thing they were trying to do was not found.
+	PerformErrorNotFound PerformErrorCode = 6
 )
 
 type PerformJoinRequest struct {
diff --git a/roomserver/internal/perform/perform_invite.go b/roomserver/internal/perform/perform_invite.go
index 08b1035fa..39f48a4a5 100644
--- a/roomserver/internal/perform/perform_invite.go
+++ b/roomserver/internal/perform/perform_invite.go
@@ -92,7 +92,7 @@ func (r *Inviter) PerformInvite(
 		}
 		if userRes.Available {
 			res.Error = &api.PerformError{
-				Code: api.PerformErrorBadRequest,
+				Code: api.PerformErrorNotFound,
 				Msg:  fmt.Sprintf("The user ID %q does not exist!", targetUserID),
 			}
 			return nil, nil