diff --git a/include/openssl/ssl.h b/include/openssl/ssl.h
index 26e504d..7cb12f1 100644
--- a/include/openssl/ssl.h
+++ b/include/openssl/ssl.h
@@ -1496,6 +1496,12 @@
  * TODO(davidben): This should return a const X509 *. */
 OPENSSL_EXPORT X509 *SSL_SESSION_get0_peer(const SSL_SESSION *session);
 
+/* SSL_SESSION_get_master_key writes up to |max_out| bytes of |session|'s master
+ * secret to |out| and returns the number of bytes written. If |max_out| is
+ * zero, it returns the size of the master secret. */
+OPENSSL_EXPORT size_t SSL_SESSION_get_master_key(const SSL_SESSION *session,
+                                                 uint8_t *out, size_t max_out);
+
 /* SSL_SESSION_set_time sets |session|'s creation time to |time| and returns
  * |time|. This function may be useful in writing tests but otherwise should not
  * be used. */