diff --git a/aes/aes.cpp b/aes/aes.cpp
index b6a25cc..10f8de7 100644
--- a/aes/aes.cpp
+++ b/aes/aes.cpp
@@ -142,7 +142,7 @@ void mixColumns(t_state s) {
 // Taken from: https://www.brainkart.com/article/AES-Key-Expansion_8410/
 void expandKey(uint8_t k[16], uint32_t ek[44]) {
     for (uint8_t i = 0; i < 4; i++) {
-        ek[i] = word(k[i], k[i + 1], k[i + 2], k[i + 3]);
+        ek[i] = word(k[i * 4], k[i * 4 + 1], k[i * 4 + 2], k[i * 4 + 3]);
     }
 
     for (uint8_t i = 4; i < 44; i++) {