diff --git a/docs/_extend_docstrings.py b/docs/_extend_docstrings.py
index 8b8457bb..e80c21c2 100644
--- a/docs/_extend_docstrings.py
+++ b/docs/_extend_docstrings.py
@@ -6,7 +6,6 @@
 # pyright: reportMissingImports=false
 from __future__ import annotations
 
-import hashlib
 import inspect
 import logging
 import pickle
@@ -24,6 +23,7 @@
 from ampform.io import aslatex
 from ampform.kinematics.lorentz import ArraySize, FourMomentumSymbol
 from ampform.sympy._array_expressions import ArrayMultiplication
+from ampform.sympy._cache import get_readable_hash
 
 if TYPE_CHECKING:
     from qrules.transition import ReactionInfo, SpinFormalism
@@ -727,7 +727,7 @@ def __generate_transitions_cached(
 ) -> ReactionInfo:
     version = get_package_version("qrules")
     obj = (initial_state, final_state, formalism)
-    h = hashlib.sha256(pickle.dumps(obj)).hexdigest()
+    h = get_readable_hash(obj)
     docs_dir = Path(__file__).parent
     file_name = docs_dir / ".cache" / f"reaction-qrules-v{version}-{h}.pickle"
     file_name.parent.mkdir(exist_ok=True)
diff --git a/src/ampform/sympy/_cache.py b/src/ampform/sympy/_cache.py
index 581b85fb..9a756ee9 100644
--- a/src/ampform/sympy/_cache.py
+++ b/src/ampform/sympy/_cache.py
@@ -45,4 +45,4 @@ def get_readable_hash(obj) -> str:
 def to_bytes(obj) -> bytes:
     if isinstance(obj, bytes | bytearray):
         return obj
-    return pickle.dumps(obj)
+    return pickle.dumps(obj, protocol=pickle.HIGHEST_PROTOCOL)
diff --git a/tests/sympy/test_cache.py b/tests/sympy/test_cache.py
index daf32ee2..41639e6e 100644
--- a/tests/sympy/test_cache.py
+++ b/tests/sympy/test_cache.py
@@ -20,9 +20,9 @@
 @pytest.mark.parametrize(
     ("expected_hash", "assumptions"),
     [
-        ("564ea466060f7565ec3ee24de64e0f92", dict()),
-        ("91495f4a4193c7ac08bd53e7fb5a1521", dict(real=True)),
-        ("dba358d78f1aec9641114d7a26d59a09", dict(rational=True)),
+        ("a7559ca6e9037446da186a62ff1ed673", dict()),
+        ("f4b1fadd65890a86cbac47da2435694d", dict(real=True)),
+        ("d5bdc74485ba4d3f16f387541315f64d", dict(rational=True)),
     ],
     ids=["symbol", "symbol-real", "symbol-rational"],
 )
@@ -50,7 +50,7 @@ def test_get_readable_hash_energy_dependent_width():
         meson_radius=d,
     )
     h = get_readable_hash(expr)
-    assert h == "2ebebe58be64f0b77540fd138597c28e"
+    assert h == "ccafec30a6b6974920652b9df1b13c57"
 
 
 class TestLargeHash:
@@ -62,8 +62,8 @@ class TestLargeHash:
     @pytest.mark.parametrize(
         ("expected_hash", "formalism"),
         [
-            ("65106a44301f9340e633d09f66ad7d17", "canonical-helicity"),
-            ("9646d3ee5c5e8534deb8019435161f2e", "helicity"),
+            ("762cc006a8c4c0a0a88fce934a32577d", "canonical-helicity"),
+            ("17fefe55a7da0810371e90bd762a176a", "helicity"),
         ],
         ids=["canonical-helicity", "helicity"],
     )
@@ -80,8 +80,8 @@ def test_reaction(self, expected_hash: str, formalism: SpinFormalism):
     @pytest.mark.parametrize(
         ("expected_hash", "formalism"),
         [
-            ("bb6cba308b7b7691c22ffa6d462f55c8", "canonical-helicity"),
-            ("1d31f62fd37c5053d498ee9b35ae4244", "helicity"),
+            ("01bb11213896fcb173cb9b4ea4bdc3bf", "canonical-helicity"),
+            ("0638a0ec2efa602e4c1f79141f7ca88a", "helicity"),
         ],
         ids=["canonical-helicity", "helicity"],
     )