diff --git a/test/freeflow/stokes/stokes-reference.hh b/test/freeflow/stokes/stokes-reference.vtu
similarity index 100%
rename from test/freeflow/stokes/stokes-reference.hh
rename to test/freeflow/stokes/stokes-reference.vtu
diff --git a/test/freeflow/stokes2c/stokes2c-reference.hh b/test/freeflow/stokes2c/stokes2c-reference.vtu
similarity index 100%
rename from test/freeflow/stokes2c/stokes2c-reference.hh
rename to test/freeflow/stokes2c/stokes2c-reference.vtu
diff --git a/test/freeflow/stokes2cni/stokes2cni-reference.hh b/test/freeflow/stokes2cni/stokes2cni-reference.vtu
similarity index 100%
rename from test/freeflow/stokes2cni/stokes2cni-reference.hh
rename to test/freeflow/stokes2cni/stokes2cni-reference.vtu