diff --git a/python/adjoint/objective.py b/python/adjoint/objective.py
index e50076a26..616353aae 100644
--- a/python/adjoint/objective.py
+++ b/python/adjoint/objective.py
@@ -216,7 +216,7 @@ def place_adjoint_source(self, dJ):
                 center=self.volume.center,
                 **self.eigenmode_kwargs,
             )
-        else isinstance(self.mode,mp.DiffractedPlanewave):
+        elif isinstance(self.mode,mp.DiffractedPlanewave):
             source = mp.EigenModeSource(
                 src,
                 eig_band=new_dp,