diff --git a/README.md b/README.md
index 44c108d..8731992 100644
--- a/README.md
+++ b/README.md
@@ -18,11 +18,11 @@ void AES_ctx_set_iv(struct AES_ctx* ctx, const uint8_t* iv);
 void AES_ECB_encrypt(const struct AES_ctx* ctx, uint8_t* buf);
 void AES_ECB_decrypt(const struct AES_ctx* ctx, uint8_t* buf);
 
-void AES_CBC_encrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
-void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
+void AES_CBC_encrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length);
+void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length);
 
 /* Same function for encrypting as for decrypting in CTR mode */
-void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length);
+void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length);
 ```
 
 Note: