diff --git a/lib/core/convert.py b/lib/core/convert.py
index bf5351030..7d619099c 100644
--- a/lib/core/convert.py
+++ b/lib/core/convert.py
@@ -33,7 +33,7 @@ def base64encode(value):
     return value.encode("base64")[:-1].replace("\n", "")
 
 def base64pickle(value):
-    return base64encode(pickle.dumps(value))
+    return base64encode(pickle.dumps(value, pickle.HIGHEST_PROTOCOL))
 
 def base64unpickle(value):
     return pickle.loads(base64decode(value))
diff --git a/lib/core/settings.py b/lib/core/settings.py
index c9f0c2c11..83346edff 100644
--- a/lib/core/settings.py
+++ b/lib/core/settings.py
@@ -446,8 +446,8 @@ DEFAULT_COOKIE_DELIMITER = ';'
 # Skip unforced HashDB flush requests below the threshold number of cached items
 HASHDB_FLUSH_THRESHOLD = 32
 
-# Unique milestone value used for forced deprecation of old HashDB values (e.g. because of changing of load/store mechanism)
-HASHDB_MILESTONE_VALUE = "4SXDcCai5n"  # r4853
+# Unique milestone value used for forced deprecation of old HashDB values (e.g. when changing hash/pickle mechanism)
+HASHDB_MILESTONE_VALUE = "EfjamfhMVw"  # r4856
 
 # Warn user of possible delay due to large page dump in full UNION query injections
 LARGE_OUTPUT_THRESHOLD = 1024**2