diff --git a/zebra-chain/src/parameters/network_upgrade.rs b/zebra-chain/src/parameters/network_upgrade.rs
index e4da0db51..132368a19 100644
--- a/zebra-chain/src/parameters/network_upgrade.rs
+++ b/zebra-chain/src/parameters/network_upgrade.rs
@@ -118,6 +118,12 @@ const TESTNET_MINIMUM_DIFFICULTY_GAP_MULTIPLIER: i32 = 6;
 /// Based on https://zips.z.cash/zip-0208#minimum-difficulty-blocks-on-the-test-network
 const TESTNET_MINIMUM_DIFFICULTY_START_HEIGHT: block::Height = block::Height(299_188);
 
+/// The activation height for the block maximum time rule on Testnet.
+///
+/// Part of the block header consensus rules in the Zcash specification at
+/// https://zips.z.cash/protocol/protocol.pdf#blockheader
+pub const TESTNET_MAX_TIME_START_HEIGHT: block::Height = block::Height(653_606);
+
 impl NetworkUpgrade {
     /// Returns a BTreeMap of activation heights and network upgrades for
     /// `network`.
@@ -274,6 +280,21 @@ impl NetworkUpgrade {
     ) -> Duration {
         NetworkUpgrade::current(network, height).averaging_window_timespan()
     }
+
+    /// Returns true if the maximum block time rule is active for `network` and `height`.
+    ///
+    /// Always returns true if `network` is the Mainnet.
+    /// If `network` is the Testnet, the `height` should be at least
+    /// TESTNET_MAX_TIME_START_HEIGHT to return true.
+    /// Returns false otherwise.
+    ///
+    /// Part of the consensus rules at https://zips.z.cash/protocol/protocol.pdf#blockheader
+    pub fn is_max_block_time_enforced(network: Network, height: block::Height) -> bool {
+        match network {
+            Network::Mainnet => true,
+            Network::Testnet => height >= TESTNET_MAX_TIME_START_HEIGHT,
+        }
+    }
 }
 
 impl ConsensusBranchId {
diff --git a/zebra-state/src/service/check.rs b/zebra-state/src/service/check.rs
index f9c580ea2..bdb8bc28c 100644
--- a/zebra-state/src/service/check.rs
+++ b/zebra-state/src/service/check.rs
@@ -5,8 +5,8 @@ use std::borrow::Borrow;
 use chrono::Duration;
 use zebra_chain::{
     block::{self, Block},
-    parameters::Network,
     parameters::POW_AVERAGING_WINDOW,
+    parameters::{Network, NetworkUpgrade},
     work::difficulty::CompactDifficulty,
 };
 
@@ -14,7 +14,7 @@ use crate::{PreparedBlock, ValidateContextError};
 
 use super::check;
 
-use difficulty::{AdjustedDifficulty, POW_MEDIAN_BLOCK_SPAN, TESTNET_MAX_TIME_START_HEIGHT};
+use difficulty::{AdjustedDifficulty, POW_MEDIAN_BLOCK_SPAN};
 
 pub(crate) mod difficulty;
 
@@ -148,7 +148,7 @@ fn difficulty_threshold_is_valid(
     }
 
     // The maximum time rule is only active on Testnet from a specific height
-    if (network == Network::Mainnet || candidate_height >= TESTNET_MAX_TIME_START_HEIGHT)
+    if NetworkUpgrade::is_max_block_time_enforced(network, candidate_height)
         && candidate_time > block_time_max
     {
         Err(ValidateContextError::TimeTooLate {
diff --git a/zebra-state/src/service/check/difficulty.rs b/zebra-state/src/service/check/difficulty.rs
index f71538f61..44bf03120 100644
--- a/zebra-state/src/service/check/difficulty.rs
+++ b/zebra-state/src/service/check/difficulty.rs
@@ -42,11 +42,6 @@ pub const POW_MAX_ADJUST_DOWN_PERCENT: i32 = 32;
 /// Part of the block header consensus rules in the Zcash specification.
 pub const BLOCK_MAX_TIME_SINCE_MEDIAN: i64 = 90 * 60;
 
-/// The activation height for the block maximum time rule on Testnet.
-///
-/// Part of the block header consensus rules in the Zcash specification.
-pub const TESTNET_MAX_TIME_START_HEIGHT: block::Height = block::Height(653_606);
-
 /// Contains the context needed to calculate the adjusted difficulty for a block.
 pub(super) struct AdjustedDifficulty {
     /// The `header.time` field from the candidate block