diff --git a/include/openssl/rsa.h b/include/openssl/rsa.h
index e44e228..e0c4368 100644
--- a/include/openssl/rsa.h
+++ b/include/openssl/rsa.h
@@ -152,7 +152,7 @@
  *
  * WARNING: this function is dangerous because it breaks the usual return value
  * convention. Use |RSA_encrypt| instead. */
-OPENSSL_EXPORT int RSA_public_encrypt(int flen, const uint8_t *from,
+OPENSSL_EXPORT int RSA_public_encrypt(size_t flen, const uint8_t *from,
                                       uint8_t *to, RSA *rsa, int padding);
 
 /* RSA_private_decrypt decrypts |flen| bytes from |from| with the public key in
@@ -244,7 +244,7 @@
  *
  * WARNING: this function is dangerous because it breaks the usual return value
  * convention. Use |RSA_sign_raw| instead. */
-OPENSSL_EXPORT int RSA_private_encrypt(int flen, const uint8_t *from,
+OPENSSL_EXPORT int RSA_private_encrypt(size_t flen, const uint8_t *from,
                                        uint8_t *to, RSA *rsa, int padding);
 
 /* RSA_public_decrypt verifies |flen| bytes of signature from |from| using the
@@ -255,7 +255,7 @@
  *
  * WARNING: this function is dangerous because it breaks the usual return value
  * convention. Use |RSA_verify_raw| instead. */
-OPENSSL_EXPORT int RSA_public_decrypt(int flen, const uint8_t *from,
+OPENSSL_EXPORT int RSA_public_decrypt(size_t flen, const uint8_t *from,
                                       uint8_t *to, RSA *rsa, int padding);