diff --git a/README.md b/README.md
index dfee426..195f102 100644
--- a/README.md
+++ b/README.md
@@ -46,6 +46,7 @@ The object associated with that key is a set of options that should be passed to
 - `NPM_PASSWORD`
 - `NPM_EMAIL`
 - `NPM_CONFIG_REGISTRY`
+- `NPM_CONFIG_USERCONFIG`
 
 For any of these variables, if you define a `{UPPER_CASE_REGISTRY_NAME}_{VARIABLE}` environment variable, it will be used instead.
 
diff --git a/index.js b/index.js
index a6d3ee4..8f0ee03 100644
--- a/index.js
+++ b/index.js
@@ -43,6 +43,7 @@ function createCallbackWrapper(callbackName) {
         'NPM_PASSWORD',
         'NPM_EMAIL',
         'NPM_CONFIG_REGISTRY',
+        'NPM_CONFIG_USERCONFIG',
       ]) {
         const overridenValue = env[environmentVariablePrefix + variableName];
         if (overridenValue) {