diff --git a/doc/man3/SSL_get_client_random.pod b/doc/man3/SSL_get_client_random.pod
index d6918f8dbe42ad2852b529223d4ca5dbc75f29c4..83a1027bcacfab906107a53b362318ab2bc3496b 100644
--- a/doc/man3/SSL_get_client_random.pod
+++ b/doc/man3/SSL_get_client_random.pod
@@ -16,7 +16,7 @@ SSL_SESSION_set1_master_key
  size_t SSL_get_server_random(const SSL *ssl, unsigned char *out, size_t outlen);
  size_t SSL_SESSION_get_master_key(const SSL_SESSION *session,
                                    unsigned char *out, size_t outlen);
- int SSL_SESSION_set1_master_key(SSL_SESSION *sess, unsigned char *in,
+ int SSL_SESSION_set1_master_key(SSL_SESSION *sess, const unsigned char *in,
                                  size_t len);
 
 =head1 DESCRIPTION
diff --git a/include/openssl/ssl.h b/include/openssl/ssl.h
index c0d3904a491deff12254d81885f745e6c5f1ec7f..75fb1fcc7ff01ceecd1b8ea46b06152466b02e3f 100644
--- a/include/openssl/ssl.h
+++ b/include/openssl/ssl.h
@@ -1865,8 +1865,8 @@ __owur size_t SSL_get_server_random(const SSL *ssl, unsigned char *out,
                                     size_t outlen);
 __owur size_t SSL_SESSION_get_master_key(const SSL_SESSION *ssl,
                                          unsigned char *out, size_t outlen);
-__owur int SSL_SESSION_set1_master_key(SSL_SESSION *sess, unsigned char *in,
-                                       size_t len);
+__owur int SSL_SESSION_set1_master_key(SSL_SESSION *sess,
+                                       const unsigned char *in, size_t len);
 
 #define SSL_get_ex_new_index(l, p, newf, dupf, freef) \
     CRYPTO_get_ex_new_index(CRYPTO_EX_INDEX_SSL, l, p, newf, dupf, freef)
diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index db14e223504a749895d2019a23bea843df647507..f9c7b4451b14c10dba7d2c700afc76adb1a91506 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -3725,7 +3725,7 @@ size_t SSL_SESSION_get_master_key(const SSL_SESSION *session,
     return outlen;
 }
 
-int SSL_SESSION_set1_master_key(SSL_SESSION *sess, unsigned char *in,
+int SSL_SESSION_set1_master_key(SSL_SESSION *sess, const unsigned char *in,
                                 size_t len)
 {
     if (len > sizeof(sess->master_key))