diff --git a/doc/release-notes.md b/doc/release-notes.md
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -11,3 +11,12 @@
 New RPC methods
 ------------
 - `getnodeaddresses` returns peer addresses known to this node. It may be used to connect to nodes over TCP without using the DNS seeds.
+
+
+Network upgrade
+---------------
+
+At the MTP time of 1589544000 (May 15, 2020 12:00:00 UTC) the following behaviors will change:
+
+- The default for max number of in-pool ancestors (`-limitancestorcount`) is changed from 25 to 50.
+- The default for max number of in-pool descendants (`-limitdescendantcount`) is changed from 25 to 50.
diff --git a/src/init.cpp b/src/init.cpp
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -743,8 +743,10 @@
                  true, OptionsCategory::DEBUG_TEST);
     gArgs.AddArg("-limitancestorcount=<n>",
                  strprintf("Do not accept transactions if number of in-mempool "
-                           "ancestors is <n> or more (default: %u)",
-                           DEFAULT_ANCESTOR_LIMIT),
+                           "ancestors is <n> or more (pre-phonon-upgrade "
+                           "default: %u, post-phonon-upgrade default: %u)",
+                           DEFAULT_ANCESTOR_LIMIT,
+                           DEFAULT_ANCESTOR_LIMIT_LONGER),
                  true, OptionsCategory::DEBUG_TEST);
     gArgs.AddArg(
         "-limitancestorsize=<n>",
@@ -755,8 +757,9 @@
     gArgs.AddArg(
         "-limitdescendantcount=<n>",
         strprintf("Do not accept transactions if any ancestor would have <n> "
-                  "or more in-mempool descendants (default: %u)",
-                  DEFAULT_DESCENDANT_LIMIT),
+                  "or more in-mempool descendants (default pre-phonon-upgrade: "
+                  "%u, default post-phonon-upgrade: %u)",
+                  DEFAULT_DESCENDANT_LIMIT, DEFAULT_DESCENDANT_LIMIT_LONGER),
         true, OptionsCategory::DEBUG_TEST);
     gArgs.AddArg(
         "-limitdescendantsize=<n>",
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -742,13 +742,15 @@
 
         // Calculate in-mempool ancestors, up to a limit.
         CTxMemPool::setEntries setAncestors;
-        size_t nLimitAncestors =
-            gArgs.GetArg("-limitancestorcount", DEFAULT_ANCESTOR_LIMIT);
+        size_t nLimitAncestors = gArgs.GetArg(
+            "-limitancestorcount",
+            GetDefaultAncestorLimit(consensusParams, chainActive.Tip()));
         size_t nLimitAncestorSize =
             gArgs.GetArg("-limitancestorsize", DEFAULT_ANCESTOR_SIZE_LIMIT) *
             1000;
-        size_t nLimitDescendants =
-            gArgs.GetArg("-limitdescendantcount", DEFAULT_DESCENDANT_LIMIT);
+        size_t nLimitDescendants = gArgs.GetArg(
+            "-limitdescendantcount",
+            GetDefaultDescendantLimit(consensusParams, chainActive.Tip()));
         size_t nLimitDescendantSize =
             gArgs.GetArg("-limitdescendantsize",
                          DEFAULT_DESCENDANT_SIZE_LIMIT) *
diff --git a/test/functional/mempool_packages.py b/test/functional/mempool_packages.py
--- a/test/functional/mempool_packages.py
+++ b/test/functional/mempool_packages.py
@@ -16,15 +16,29 @@
     sync_mempools,
 )
 
-MAX_ANCESTORS = 25
-MAX_DESCENDANTS = 25
+# TODO: The activation code can be reverted after the new policy becomes
+# active.
+
+# Phonon dummy activation time
+ACTIVATION_TIME = 2000000000
+
+# Replay protection time needs to be moved beyond phonon activation
+REPLAY_PROTECTION_TIME = ACTIVATION_TIME * 2
+
+MAX_ANCESTORS = 50
+MAX_DESCENDANTS = 50
 
 
 class MempoolPackagesTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
-        self.extra_args = [["-maxorphantx=1000"],
-                           ["-maxorphantx=1000", "-limitancestorcount=5"]]
+
+        common_params = ["-maxorphantx=1000",
+                         "-phononactivationtime={}".format(ACTIVATION_TIME),
+                         "-replayprotectionactivationtime={}".format(REPLAY_PROTECTION_TIME)]
+
+        self.extra_args = [common_params,
+                           common_params + ["-limitancestorcount=5"]]
 
     def skip_test_if_missing_module(self):
         self.skip_if_no_wallet()
@@ -47,6 +61,8 @@
         return (txid, send_value)
 
     def run_test(self):
+        [n.setmocktime(ACTIVATION_TIME) for n in self.nodes]
+
         # Mine some blocks and have them mature.
         self.nodes[0].generate(101)
         utxo = self.nodes[0].listunspent(10)