diff --git a/patchdiff/serialize.py b/patchdiff/serialize.py
index 1bcf6b1..e2eab68 100644
--- a/patchdiff/serialize.py
+++ b/patchdiff/serialize.py
@@ -3,10 +3,7 @@
 
 
 def to_str_paths(ops: List) -> List:
-    str_ops = ops.copy()
-    for op in str_ops:
-        op["path"] = str(op["path"])
-    return str_ops
+    return [{**op, "path": str(op["path"])} for op in ops]
 
 
 def to_json(ops: List, **kwargs) -> str:
diff --git a/tests/test_serialize.py b/tests/test_serialize.py
index 0665cdb..e2ebef2 100644
--- a/tests/test_serialize.py
+++ b/tests/test_serialize.py
@@ -1,4 +1,14 @@
-from patchdiff import diff, to_json
+from patchdiff import apply, diff, to_json
+
+
+def test_to_json_does_not_mutate_ops():
+    a = {"x": [1, 2, 3]}
+    b = {"x": [1, 9, 3]}
+    ops, _ = diff(a, b)
+
+    to_json(ops)
+
+    assert apply(a, ops) == b
 
 
 def test_to_json():