diff --git a/test/c++/gfs/mpi_gf.cpp b/test/c++/gfs/mpi_gf.cpp
index cc151cb62..8dbd34668 100644
--- a/test/c++/gfs/mpi_gf.cpp
+++ b/test/c++/gfs/mpi_gf.cpp
@@ -131,10 +131,10 @@ TEST_F(MpiGf, ReduceBlockView) {
 
   auto bgf2 = bgf;
 
-  bgf2() = mpi::reduce(bgf);
+  bgf2 = mpi::reduce(bgf);
   if (world.rank() == 0) test_gfs_are_close(bgf2[0], gf<imfreq>{world.size() * g1});
 
-  bgf2() = mpi::all_reduce(bgf);
+  bgf2 = mpi::all_reduce(bgf);
   test_gfs_are_close(bgf2[0], gf<imfreq>{world.size() * g1});
 }