diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -3,6 +3,7 @@
 # Fānyì (翻译)
 
 A 🇨🇳 and 🇺🇸🇬🇧 translator in your command line, powered by iciba and groq.
+Ensure that the GROQ_API_KEY is set in your environment variables.
 
 [![NPM version][npm-image]][npm-url]
 [![npm download][download-image]][download-url]