diff --git a/src/credentials.ts b/src/credentials.ts
index ed54e86..7c59e6a 100644
--- a/src/credentials.ts
+++ b/src/credentials.ts
@@ -34,10 +34,13 @@ export interface Config {
  */
 function expandPath(filePath: string): string {
   // Expand environment variables: ${VAR} and $VAR formats
-  let expanded = filePath.replace(/\$\{([^}]+)\}|\$([A-Za-z_][A-Za-z0-9_]*)/g, (_, braced, bare) => {
-    const variable = braced || bare;
-    return process.env[variable] || '';
-  });
+  let expanded = filePath.replace(
+    /\$\{([^}]+)\}|\$([A-Za-z_][A-Za-z0-9_]*)/g,
+    (_, braced: string | undefined, bare: string | undefined) => {
+      const variable = braced || bare || '';
+      return process.env[variable] || '';
+    }
+  );
 
   // Handle tilde for home directory
   if (expanded.startsWith('~/')) {
@@ -145,6 +148,7 @@ export function saveConfig(config: Config, filePath: string): void {
   const expandedPath = expandPath(filePath);
 
   // Strip internal field before dumping
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
   const { _rawContent, ...configData } = config;
 
   const yamlContent = yaml.dump(configData, {