diff --git a/pandas/tests/frame/indexing/test_where.py b/pandas/tests/frame/indexing/test_where.py
index e23a893e0538d..eaafd2f017e79 100644
--- a/pandas/tests/frame/indexing/test_where.py
+++ b/pandas/tests/frame/indexing/test_where.py
@@ -771,3 +771,13 @@ def test_where_non_keyword_deprecation():
         result = s.where(s > 1, 10, False)
     expected = DataFrame([10, 10, 2, 3, 4])
     tm.assert_frame_equal(expected, result)
+
+
+def test_where_columns_casting():
+    # GH 42295
+
+    df = DataFrame({"a": [1.0, 2.0], "b": [3, np.nan]})
+    expected = df.copy()
+    result = df.where(pd.notnull(df), None)
+    # make sure dtypes don't change
+    tm.assert_frame_equal(expected, result)