diff --git a/openssl-sys/src/lib.rs b/openssl-sys/src/lib.rs
index f5de44b6..ca1148d4 100644
--- a/openssl-sys/src/lib.rs
+++ b/openssl-sys/src/lib.rs
@@ -1471,7 +1471,7 @@ extern {
     pub fn PEM_read_bio_RSAPrivateKey(bio: *mut BIO, rsa: *mut *mut RSA, callback: Option<PasswordCallback>, user_data: *mut c_void) -> *mut RSA;
     pub fn PEM_read_bio_RSA_PUBKEY(bio:    *mut BIO, rsa: *mut *mut RSA, callback: Option<PasswordCallback>, user_data: *mut c_void) -> *mut RSA;
 
-    pub fn PEM_write_bio_DHparams(bio: *mut BIO, x: *mut DH) -> c_int;
+    pub fn PEM_write_bio_DHparams(bio: *mut BIO, x: *const DH) -> c_int;
     pub fn PEM_write_bio_PrivateKey(bio: *mut BIO, pkey: *mut EVP_PKEY, cipher: *const EVP_CIPHER,
                                     kstr: *mut c_uchar, klen: c_int,
                                     callback: Option<PasswordCallback>,