diff --git a/src/ptpython/printer.py b/src/ptpython/printer.py
index a3578de..5b5ae45 100644
--- a/src/ptpython/printer.py
+++ b/src/ptpython/printer.py
@@ -152,8 +152,19 @@ def _format_result_output(
                 formatted_result_repr = to_formatted_text(
                     getattr(result, "__pt_repr__")()
                 )
-                yield from formatted_result_repr
-                return
+                # Only trust the result if every fragment is a well-formed
+                # ``(style, text)`` tuple. A `unittest.mock.MagicMock` (and
+                # similar auto-attribute objects) fabricates a `__pt_repr__`
+                # that resolves to more mocks, so `to_formatted_text` can yield
+                # malformed fragments such as an empty tuple, which would later
+                # crash `split_lines` with a "not enough values to unpack"
+                # `ValueError`. Fall back to the normal `repr()` path instead.
+                if all(
+                    isinstance(fragment, tuple) and len(fragment) >= 2
+                    for fragment in formatted_result_repr
+                ):
+                    yield from formatted_result_repr
+                    return
         except (GeneratorExit, KeyboardInterrupt):
             raise  # Don't catch here.
         except:
diff --git a/tests/test_printer.py b/tests/test_printer.py
new file mode 100644
index 0000000..358e3f2
--- /dev/null
+++ b/tests/test_printer.py
@@ -0,0 +1,42 @@
+from __future__ import annotations
+
+from unittest.mock import MagicMock
+
+from prompt_toolkit.formatted_text.utils import split_lines
+
+from ptpython.printer import OutputPrinter
+
+
+def test_format_result_output_handles_mock_with_fabricated_pt_repr() -> None:
+    """A ``unittest.mock.MagicMock`` fabricates any attribute, including
+    ``__pt_repr__``, which resolves to more mocks. ``to_formatted_text`` then
+    yields malformed fragments (e.g. an empty tuple) that used to crash
+    ``split_lines`` with ``ValueError: not enough values to unpack``. The
+    printer must fall back to the normal ``repr()`` path instead. See #610.
+    """
+    mock = MagicMock()
+    mock.get()
+    call = mock.method_calls[0]
+
+    printer = OutputPrinter.__new__(OutputPrinter)
+    fragments = list(
+        printer._format_result_output(
+            call,
+            reformat=False,
+            highlight=True,
+            line_length=80,
+            paginate=False,
+        )
+    )
+
+    # Every fragment must be a well-formed (style, text) tuple, so splitting
+    # into lines does not raise.
+    for fragment in fragments:
+        assert isinstance(fragment, tuple)
+        assert len(fragment) >= 2
+    list(split_lines(fragments))
+
+    # The fallback renders the object's ``repr`` rather than the mock's
+    # fabricated formatted text.
+    rendered = "".join(text for _, text, *_ in fragments)
+    assert "call" in rendered