diff --git a/lib/hkdf.js b/lib/hkdf.js
index 6314d0c..7a87417 100644
--- a/lib/hkdf.js
+++ b/lib/hkdf.js
@@ -14,7 +14,7 @@ function zeros(length) {
 
   return buf.toString();
 }
-// imk is initial keying material
+// ikm is initial keying material
 function HKDF(hashAlg, salt, ikm) {
   this.hashAlg = hashAlg;
 
@@ -49,4 +49,4 @@ HKDF.prototype = {
   }
 };
 
-module.exports = HKDF;
\ No newline at end of file
+module.exports = HKDF;