change from unsigned size_t to size_t since size_t is always defined as unsigned.
diff --git a/cryptography/hazmat/bindings/openssl/aes.py b/cryptography/hazmat/bindings/openssl/aes.py
index fa8cbc7..58ef0cf 100644
--- a/cryptography/hazmat/bindings/openssl/aes.py
+++ b/cryptography/hazmat/bindings/openssl/aes.py
@@ -43,7 +43,7 @@
this in 1.0.0+. It is defined in macros because the function signature
changed after 0.9.8 */
void AES_ctr128_encrypt(const unsigned char *, unsigned char *,
- const unsigned size_t, const AES_KEY *,
+ const size_t, const AES_KEY *,
unsigned char[], unsigned char[], unsigned int *);
"""