diff --git a/lib/rest.js b/lib/rest.js
index 8b19c69..a5eb654 100644
--- a/lib/rest.js
+++ b/lib/rest.js
@@ -67,7 +67,8 @@ class RestClient {
     // Only apply proxy agents if custom agents are not explicitly provided
     // Priority: explicit httpsAgent/httpAgent > proxy config > default
     const hasCustomAgents =
-      'httpsAgent' in this.restClientConfig || 'httpAgent' in this.restClientConfig;
+      this.restClientConfig &&
+      ('httpsAgent' in this.restClientConfig || 'httpAgent' in this.restClientConfig);
     const proxyAgents = hasCustomAgents ? {} : getProxyAgentForUrl(url, this.restClientConfig);
 
     return this.axiosInstance