diff --git a/src/client.ts b/src/client.ts
index 042ff71..4b65082 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -12,7 +12,7 @@ import {
 } from 'node:tls';
 import { EventEmitter } from 'node:events';
 
-import { Defaults, Environment } from './defaults.js';
+import { Defaults } from './defaults.js';
 import * as logger from './logging.js';
 
 import { postgresqlErrorCodes } from './errors.js';
@@ -147,7 +147,7 @@ interface PreFlightQueue {
     bind: Bind | null;
 }
 
-const DEFAULTS = new Defaults(env as unknown as Environment);
+const DEFAULTS = new Defaults(env as Record<string, string>);
 
 export type EventMap<
     T = {
diff --git a/src/defaults.ts b/src/defaults.ts
index c03053d..8616c1b 100644
--- a/src/defaults.ts
+++ b/src/defaults.ts
@@ -4,7 +4,7 @@ import { userInfo } from 'node:os';
  *
  *  See {@link https://www.postgresql.org/docs/current/libpq-envars.html} for a detailed description.
  */
-export interface Environment {
+export type Environment = keyof {
     PGCLIENTENCODING: string;
     PGCONNECT_TIMEOUT: string;
     PGDATABASE: string;
@@ -23,7 +23,7 @@ function secToMsec(value?: number) {
 
 export class Defaults {
     constructor(
-        env: Environment,
+        env: Partial<Record<Environment, string>>,
         readonly host = env.PGHOST || 'localhost',
         readonly port = parseInt(env.PGPORT as string, 10) || 5432,
         readonly user = env.PGUSER || userInfo().username,