diff --git a/crates/polars-core/src/chunked_array/ops/full.rs b/crates/polars-core/src/chunked_array/ops/full.rs
index ee307cc3ca8e..e33d38118891 100644
--- a/crates/polars-core/src/chunked_array/ops/full.rs
+++ b/crates/polars-core/src/chunked_array/ops/full.rs
@@ -128,14 +128,21 @@ impl ArrayChunked {
             ArrowDataType::FixedSizeList(
                 Box::new(ArrowField::new(
                     PlSmallStr::from_static("item"),
-                    inner_dtype.to_arrow(CompatLevel::newest()),
+                    inner_dtype.to_physical().to_arrow(CompatLevel::newest()),
                     true,
                 )),
                 width,
             ),
             length,
         );
-        ChunkedArray::with_chunk(name, arr)
+        // SAFETY: physical type matches the logical.
+        unsafe {
+            ChunkedArray::from_chunks_and_dtype(
+                name,
+                vec![Box::new(arr)],
+                DataType::Array(Box::new(inner_dtype.clone()), width),
+            )
+        }
     }
 }
 
@@ -147,14 +154,22 @@ impl ChunkFull<&Series> for ArrayChunked {
         let arrow_dtype = ArrowDataType::FixedSizeList(
             Box::new(ArrowField::new(
                 PlSmallStr::from_static("item"),
-                dtype.to_arrow(CompatLevel::newest()),
+                dtype.to_physical().to_arrow(CompatLevel::newest()),
                 true,
             )),
             width,
         );
         let value = value.rechunk().chunks()[0].clone();
         let arr = FixedSizeListArray::full(length, value, arrow_dtype);
-        ChunkedArray::with_chunk(name, arr)
+
+        // SAFETY: physical type matches the logical.
+        unsafe {
+            ChunkedArray::from_chunks_and_dtype(
+                name,
+                vec![Box::new(arr)],
+                DataType::Array(Box::new(dtype.clone()), width),
+            )
+        }
     }
 }
 
diff --git a/py-polars/tests/unit/datatypes/test_array.py b/py-polars/tests/unit/datatypes/test_array.py
index 03f92bd68d11..6c4f240803bf 100644
--- a/py-polars/tests/unit/datatypes/test_array.py
+++ b/py-polars/tests/unit/datatypes/test_array.py
@@ -327,3 +327,18 @@ def test_array_inner_recursive_python_dtype() -> None:
 def test_array_missing_shape() -> None:
     with pytest.raises(TypeError):
         pl.Array(pl.Int8)
+
+
+def test_array_invalid_physical_type_18920() -> None:
+    s1 = pl.Series("x", [[1000, 2000]], pl.List(pl.Datetime))
+    s2 = pl.Series("x", [None], pl.List(pl.Datetime))
+
+    df1 = s1.to_frame().with_columns(pl.col.x.list.to_array(2))
+    df2 = s2.to_frame().with_columns(pl.col.x.list.to_array(2))
+
+    df = pl.concat([df1, df2])
+
+    expected_s = pl.Series("x", [[1000, 2000], None], pl.List(pl.Datetime))
+
+    expected = expected_s.to_frame().with_columns(pl.col.x.list.to_array(2))
+    assert_frame_equal(df, expected)