diff --git a/doc/release-notes-29775.md b/doc/release-notes-29775.md
new file mode 100644
index 00000000000..6cb3ed3e8d1
--- /dev/null
+++ b/doc/release-notes-29775.md
@@ -0,0 +1,10 @@
+Testnet4/BIP94 support
+-----
+
+Support for Testnet4 as specified in [BIP94](https://github.com/bitcoin/bips/blob/master/bip-0094.mediawiki)
+has been added. The network can be selected with the `-testnet4` option and
+the section header is also named `[testnet4]`.
+
+While the intention is to phase out support for Testnet3 in an upcoming
+version, support for it is still available via the known options in this
+release.
diff --git a/src/chainparamsbase.cpp b/src/chainparamsbase.cpp
index 2b57b4ca551..1c1b97430b9 100644
--- a/src/chainparamsbase.cpp
+++ b/src/chainparamsbase.cpp
@@ -17,7 +17,7 @@ void SetupChainParamsBaseOptions(ArgsManager& argsman)
     argsman.AddArg("-regtest", "Enter regression test mode, which uses a special chain in which blocks can be solved instantly. "
                  "This is intended for regression testing tools and app development. Equivalent to -chain=regtest.", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-testactivationheight=name@height.", "Set the activation height of 'name' (segwit, bip34, dersig, cltv, csv). (regtest-only)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
-    argsman.AddArg("-testnet", "Use the testnet3 chain. Equivalent to -chain=test. Support for testnet3 is deprecated and will be removed with the next release. Consider moving to testnet4 now by using -testnet4.", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
+    argsman.AddArg("-testnet", "Use the testnet3 chain. Equivalent to -chain=test. Support for testnet3 is deprecated and will be removed in an upcoming release. Consider moving to testnet4 now by using -testnet4.", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-testnet4", "Use the testnet4 chain. Equivalent to -chain=testnet4.", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-vbparams=deployment:start:end[:min_activation_height]", "Use given start/end times and min_activation_height for specified version bits deployment (regtest-only)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-signet", "Use the signet chain. Equivalent to -chain=signet. Note that the network is defined by the -signetchallenge parameter", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
diff --git a/src/kernel/chainparams.cpp b/src/kernel/chainparams.cpp
index bbddc3dfec9..d0de3a4eab6 100644
--- a/src/kernel/chainparams.cpp
+++ b/src/kernel/chainparams.cpp
@@ -334,7 +334,7 @@ public:
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
         consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 0; // No activation delay
 
-        consensus.nMinimumChainWork = uint256{};
+        consensus.nMinimumChainWork = uint256{"000000000000000000000000000000000000000000000056faca98a0cd9bdf5f"};
         consensus.defaultAssumeValid = uint256{};
 
         pchMessageStart[0] = 0x1c;
diff --git a/src/validation.cpp b/src/validation.cpp
index cf4dce3762f..ca4480aa804 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -107,6 +107,21 @@ const std::vector<std::string> CHECKLEVEL_DOC {
  * */
 static constexpr int PRUNE_LOCK_BUFFER{10};
 
+/**
+ * Maximum number of seconds that the timestamp of the first
+ * block of a difficulty adjustment period is allowed to
+ * be earlier than the last block of the previous period (BIP94).
+ */
+static constexpr int64_t MAX_TIMEWARP{MAX_FUTURE_BLOCK_TIME};
+
+/**
+ * If the timestamp of the last block in a difficulty period is set
+ * MAX_FUTURE_BLOCK_TIME seconds in the future, an honest miner should
+ * be able to mine the first block using the current time. This is not
+ * a consensus rule, but changing MAX_TIMEWARP should be done with caution.
+ */
+static_assert(MAX_FUTURE_BLOCK_TIME <= MAX_TIMEWARP);
+
 GlobalMutex g_best_block_mutex;
 std::condition_variable g_best_block_cv;
 uint256 g_best_block;
@@ -4188,7 +4203,7 @@ static bool ContextualCheckBlockHeader(const CBlockHeader& block, BlockValidatio
         // Check timestamp for the first block of each difficulty adjustment
         // interval, except the genesis block.
         if (nHeight % consensusParams.DifficultyAdjustmentInterval() == 0) {
-            if (block.GetBlockTime() < pindexPrev->GetBlockTime() - 60 * 60 * 2) {
+            if (block.GetBlockTime() < pindexPrev->GetBlockTime() - MAX_TIMEWARP) {
                 return state.Invalid(BlockValidationResult::BLOCK_INVALID_HEADER, "time-timewarp-attack", "block's timestamp is too early on diff adjustment block");
             }
         }