diff --git a/include/openssl/ecdsa.h b/include/openssl/ecdsa.h
index 3890744..8a158b8 100644
--- a/include/openssl/ecdsa.h
+++ b/include/openssl/ecdsa.h
@@ -75,7 +75,7 @@
  * zero otherwise. */
 OPENSSL_EXPORT int ECDSA_sign(int type, const uint8_t *digest,
                               size_t digest_len, uint8_t *sig,
-                              unsigned int *sig_len, EC_KEY *key);
+                              unsigned int *sig_len, const EC_KEY *key);
 
 /* ECDSA_verify verifies that |sig_len| bytes from |sig| constitute a valid
  * signature by |key| of |digest|. (The |type| argument should be zero.) It
@@ -83,7 +83,7 @@
  * occurred. */
 OPENSSL_EXPORT int ECDSA_verify(int type, const uint8_t *digest,
                                 size_t digest_len, const uint8_t *sig,
-                                size_t sig_len, EC_KEY *key);
+                                size_t sig_len, const EC_KEY *key);
 
 /* ECDSA_size returns the maximum size of an ECDSA signature using |key|. It
  * returns zero on error. */
@@ -109,13 +109,13 @@
 /* ECDSA_do_sign signs |digest_len| bytes from |digest| with |key| and returns
  * the resulting signature structure, or NULL on error. */
 OPENSSL_EXPORT ECDSA_SIG *ECDSA_do_sign(const uint8_t *digest,
-                                        size_t digest_len, EC_KEY *key);
+                                        size_t digest_len, const EC_KEY *key);
 
 /* ECDSA_do_verify verifies that |sig| constitutes a valid signature by |key|
  * of |digest|. It returns one on success or zero if the signature is invalid
  * or on error. */
 OPENSSL_EXPORT int ECDSA_do_verify(const uint8_t *digest, size_t digest_len,
-                                   const ECDSA_SIG *sig, EC_KEY *key);
+                                   const ECDSA_SIG *sig, const EC_KEY *key);
 
 
 /* Signing with precomputation.
@@ -128,22 +128,22 @@
 /* ECDSA_sign_setup precomputes parts of an ECDSA signing operation. It sets
  * |*kinv| and |*rp| to the precomputed values and uses the |ctx| argument, if
  * not NULL. It returns one on success and zero otherwise. */
-OPENSSL_EXPORT int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv,
-                                    BIGNUM **rp);
+OPENSSL_EXPORT int ECDSA_sign_setup(const EC_KEY *eckey, BN_CTX *ctx,
+                                    BIGNUM **kinv, BIGNUM **rp);
 
 /* ECDSA_do_sign_ex is the same as |ECDSA_do_sign| but takes precomputed values
  * as generated by |ECDSA_sign_setup|. */
 OPENSSL_EXPORT ECDSA_SIG *ECDSA_do_sign_ex(const uint8_t *digest,
                                            size_t digest_len,
                                            const BIGNUM *kinv, const BIGNUM *rp,
-                                           EC_KEY *eckey);
+                                           const EC_KEY *eckey);
 
 /* ECDSA_sign_ex is the same as |ECDSA_sign| but takes precomputed values as
  * generated by |ECDSA_sign_setup|. */
 OPENSSL_EXPORT int ECDSA_sign_ex(int type, const uint8_t *digest,
                                  size_t digest_len, uint8_t *sig,
                                  unsigned int *sig_len, const BIGNUM *kinv,
-                                 const BIGNUM *rp, EC_KEY *eckey);
+                                 const BIGNUM *rp, const EC_KEY *eckey);
 
 
 /* ASN.1 functions. */