diff --git a/cbits/aes/gf.c b/cbits/aes/gf.c
index 7dcc12c..3d872ae 100644
--- a/cbits/aes/gf.c
+++ b/cbits/aes/gf.c
@@ -39,7 +39,7 @@
  * to speed up the multiplication.
  * TODO: optimise with tables
  */
-void cryptonite_aes_generic_gf_mul(block128 *a, block128 *b)
+void cryptonite_aes_generic_gf_mul(block128 *a, const block128 *b)
 {
 	uint64_t a0, a1, v0, v1;
 	int i, j;
diff --git a/cbits/aes/gf.h b/cbits/aes/gf.h
index 21b542c..4a65edb 100644
--- a/cbits/aes/gf.h
+++ b/cbits/aes/gf.h
@@ -32,7 +32,7 @@
 
 #include "aes/block128.h"
 
-void cryptonite_aes_generic_gf_mul(block128 *a, block128 *b);
+void cryptonite_aes_generic_gf_mul(block128 *a, const block128 *b);
 void cryptonite_aes_generic_gf_mulx(block128 *a);
 
 #endif
diff --git a/cbits/aes/x86ni.c b/cbits/aes/x86ni.c
index bc3af2d..7049fd1 100644
--- a/cbits/aes/x86ni.c
+++ b/cbits/aes/x86ni.c
@@ -231,7 +231,7 @@ static __m128i gfmul_pclmuldq(__m128i a, __m128i b)
 	return _mm_shuffle_epi8(tmp6, bswap_mask);
 }
 
-void cryptonite_aesni_gf_mul(block128 *a, block128 *b)
+void cryptonite_aesni_gf_mul(block128 *a, const block128 *b)
 {
 	__m128i _a, _b, _c;
 	_a = _mm_loadu_si128((__m128i *) a);
@@ -240,7 +240,7 @@ void cryptonite_aesni_gf_mul(block128 *a, block128 *b)
 	_mm_storeu_si128((__m128i *) a, _c);
 }
 
-void cryptonite_aesni_init_pclmul()
+void cryptonite_aesni_init_pclmul(void)
 {
 	gfmul_branch_ptr = gfmul_pclmuldq;
 }
diff --git a/cbits/aes/x86ni.h b/cbits/aes/x86ni.h
index b9a568a..9e2898e 100644
--- a/cbits/aes/x86ni.h
+++ b/cbits/aes/x86ni.h
@@ -73,8 +73,8 @@ void cryptonite_aesni_gcm_encrypt128(uint8_t *out, aes_gcm *gcm, aes_key *key, u
 void cryptonite_aesni_gcm_encrypt256(uint8_t *out, aes_gcm *gcm, aes_key *key, uint8_t *in, uint32_t length);
 
 #ifdef WITH_PCLMUL
-void cryptonite_aesni_init_pclmul();
-void cryptonite_aesni_gf_mul(block128 *a, block128 *b);
+void cryptonite_aesni_init_pclmul(void);
+void cryptonite_aesni_gf_mul(block128 *a, const block128 *b);
 #endif
 
 #endif
diff --git a/cbits/cryptonite_aes.c b/cbits/cryptonite_aes.c
index b5ce004..f04fbc7 100644
--- a/cbits/cryptonite_aes.c
+++ b/cbits/cryptonite_aes.c
@@ -156,7 +156,7 @@ typedef void (*gcm_crypt_f)(uint8_t *output, aes_gcm *gcm, aes_key *key, uint8_t
 typedef void (*ocb_crypt_f)(uint8_t *output, aes_ocb *ocb, aes_key *key, uint8_t *input, uint32_t length);
 typedef void (*ccm_crypt_f)(uint8_t *output, aes_ccm *ccm, aes_key *key, uint8_t *input, uint32_t length);
 typedef void (*block_f)(aes_block *output, aes_key *key, aes_block *input);
-typedef void (*gf_mul_f)(aes_block *a, aes_block *b);
+typedef void (*gf_mul_f)(aes_block *a, const aes_block *b);
 
 #ifdef WITH_AESNI
 #define GET_INIT(strength) \