diff --git a/src/pymatgen/io/vasp/inputs.py b/src/pymatgen/io/vasp/inputs.py
index 4d572bcd17..ca25b04a9e 100644
--- a/src/pymatgen/io/vasp/inputs.py
+++ b/src/pymatgen/io/vasp/inputs.py
@@ -3101,7 +3101,7 @@ def __str__(self) -> str:
 
     def as_dict(self) -> dict:
         """MSONable dict."""
-        dct = {key: val.as_dict() for key, val in self.items()}
+        dct = {key: val.as_dict() if hasattr(val, "as_dict") else val for key, val in self.items()}
         dct["@module"] = type(self).__module__
         dct["@class"] = type(self).__name__
         return dct
@@ -3115,10 +3115,13 @@ def from_dict(cls, dct: dict) -> Self:
         Returns:
             VaspInput
         """
-        sub_dct: dict[str, dict] = {"optional_files": {}}
+        sub_dct: dict[str, Any] = {"optional_files": {}}
         for key, val in dct.items():
             if key in ("INCAR", "POSCAR", "POTCAR", "KPOINTS"):
                 sub_dct[key.lower()] = MontyDecoder().process_decoded(val)
+            elif key == "POTCAR.spec":
+                sub_dct["potcar"] = val
+                sub_dct["potcar_spec"] = True
             elif key not in ["@module", "@class"]:
                 sub_dct["optional_files"][key] = MontyDecoder().process_decoded(val)
         return cls(**sub_dct)  # type: ignore[arg-type]
diff --git a/tests/io/vasp/test_inputs.py b/tests/io/vasp/test_inputs.py
index 7ed9b093d4..7c8006ad35 100644
--- a/tests/io/vasp/test_inputs.py
+++ b/tests/io/vasp/test_inputs.py
@@ -2002,6 +2002,24 @@ def test_input_attr(self):
         vis_potcar_spec.incar["NSW"] = 100
         assert vis_potcar_spec.incar["NSW"] == 100
 
+    def test_as_from_dict_potcar_spec(self):
+        vis_potcar_spec = VaspInput(
+            self.vasp_input.incar,
+            self.vasp_input.kpoints,
+            self.vasp_input.poscar,
+            "\n".join(self.vasp_input.potcar.symbols),
+            potcar_spec=True,
+        )
+        # as_dict should not raise when potcar_spec=True
+        dct = vis_potcar_spec.as_dict()
+
+        # round-trip should preserve potcar_spec structure
+        roundtripped = VaspInput.from_dict(dct)
+        assert {*roundtripped} == {"INCAR", "KPOINTS", "POSCAR", "POTCAR.spec"}
+        assert isinstance(roundtripped.potcar, str)
+        assert roundtripped["POTCAR.spec"] == vis_potcar_spec["POTCAR.spec"]
+        assert roundtripped["INCAR"] == vis_potcar_spec["INCAR"]
+
 
 def test_potcar_summary_stats() -> None:
     potcar_summary_stats = loadfn(POTCAR_STATS_PATH)