diff --git a/README.md b/README.md
index e32e25e..6986064 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 This is a small and portable implementation of the AES [ECB](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Electronic_Codebook_.28ECB.29), [CTR](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_.28CTR.29) and [CBC](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_Block_Chaining_.28CBC.29) encryption algorithms written in C.
 
-You can override the default key-size of 128 bit with 192 or 256 bit by defining the symbols AES192 or AES256 in `aes.h`.
+You can override the default key-size of 128 bit with 192 or 256 bit by defining the symbols AES192 or AES256 in [`aes.h`](https://github.com/kokke/tiny-AES-c/blob/master/aes.h).
 
 The API is very simple and looks like this (I am using C99 `<stdint.h>`-style annotated types):