diff --git a/spec/src/consensus.rs b/spec/src/consensus.rs
index 1627c483f6..ede01dd5c0 100644
--- a/spec/src/consensus.rs
+++ b/spec/src/consensus.rs
@@ -824,16 +824,15 @@ impl Consensus {
                     epoch_duration_in_milliseconds,
                 } => {
                     if self.permanent_difficulty() {
+                        let next_epoch_length = (self.epoch_duration_target() + MIN_BLOCK_INTERVAL
+                            - 1)
+                            / MIN_BLOCK_INTERVAL;
                         let primary_epoch_reward =
                             self.primary_epoch_reward_of_next_epoch(&epoch).as_u64();
                         let block_reward =
-                            Capacity::shannons(primary_epoch_reward / epoch.length());
+                            Capacity::shannons(primary_epoch_reward / next_epoch_length);
                         let remainder_reward =
-                            Capacity::shannons(primary_epoch_reward % epoch.length());
-
-                        let next_epoch_length = (self.epoch_duration_target() + MIN_BLOCK_INTERVAL
-                            - 1)
-                            / MIN_BLOCK_INTERVAL;
+                            Capacity::shannons(primary_epoch_reward % next_epoch_length);
 
                         let dummy_epoch_ext = epoch
                             .clone()