diff --git a/src/gsim/palace/models/problems.py b/src/gsim/palace/models/problems.py
index 65261376..0ba1e6b4 100644
--- a/src/gsim/palace/models/problems.py
+++ b/src/gsim/palace/models/problems.py
@@ -322,10 +322,11 @@ def to_palace_config(self) -> dict:
             "Freq": self.freq / 1e9,
             "N": self.num_modes,
             "Save": self.save,
-            "Target": self.target,
             "Tol": self.tolerance,
             "Type": self.solver_type,
         }
+        if self.target > 0:  # Palace requires Target > 0 when present; 0 means auto
+            config["Target"] = self.target
         if (
             self.max_size > 0
         ):  # Even when the default is zero, passing it explicitly makes Palace fail
diff --git a/tests/palace/test_boundarymode_models.py b/tests/palace/test_boundarymode_models.py
index efc6e027..d346d969 100644
--- a/tests/palace/test_boundarymode_models.py
+++ b/tests/palace/test_boundarymode_models.py
@@ -53,3 +53,9 @@ def test_to_palace_config(self):
         assert result["MaxSize"] == 80
         assert result["Type"] == "SLEPc"
         assert "Attributes" not in result
+
+    def test_to_palace_config_omits_auto_target(self):
+        """target=0 means automatic shift, so Target is left out of the config."""
+        result = BoundaryModeConfig(freq=50e9, num_modes=2, save=2).to_palace_config()
+        assert "Target" not in result
+        assert "MaxSize" not in result