diff --git a/src/OpenSSL/SSL.py b/src/OpenSSL/SSL.py
index d809743..8a54994 100644
--- a/src/OpenSSL/SSL.py
+++ b/src/OpenSSL/SSL.py
@@ -1080,7 +1080,8 @@
 
         dh = _lib.PEM_read_bio_DHparams(bio, _ffi.NULL, _ffi.NULL, _ffi.NULL)
         dh = _ffi.gc(dh, _lib.DH_free)
-        _lib.SSL_CTX_set_tmp_dh(self._context, dh)
+        res = _lib.SSL_CTX_set_tmp_dh(self._context, dh)
+        _openssl_assert(res == 1)
 
     def set_tmp_ecdh(self, curve):
         """