diff --git a/CHANGELOG.md b/CHANGELOG.md
index c74c1bb..e753178 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,5 @@
+### Fixed
+- Client errors when the `restClientConfig` not specified.
 
 ## [5.5.0] - 2025-10-28
 ### Added
diff --git a/VERSION b/VERSION
index d50359d..1f5ac30 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-5.5.0
+5.5.1-SNAPSHOT
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
diff --git a/version_fragment b/version_fragment
index acb503f..9eb7b90 100644
--- a/version_fragment
+++ b/version_fragment
@@ -1 +1 @@
-minor
+patch