diff --git a/CHANGELOG.md b/CHANGELOG.md
index f85ed6526b..9007e510ad 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,8 @@ and this project adheres to the versioning scheme outlined in the [README.md](RE
 
 ### Added
 
+- Set the epoch to 3.1 in the Clarity DB upon activation.
+
 ### Changed
 
 ## [3.1.0.0.1]
diff --git a/stackslib/src/chainstate/nakamoto/mod.rs b/stackslib/src/chainstate/nakamoto/mod.rs
index 35f6e5d1e1..adf9dddc0e 100644
--- a/stackslib/src/chainstate/nakamoto/mod.rs
+++ b/stackslib/src/chainstate/nakamoto/mod.rs
@@ -3937,7 +3937,11 @@ impl NakamotoChainState {
 
         // is this stacks block the first of a new epoch?
         let (applied_epoch_transition, mut tx_receipts) =
-            StacksChainState::process_epoch_transition(&mut clarity_tx, burn_header_height)?;
+            StacksChainState::process_epoch_transition(
+                &mut clarity_tx,
+                sortition_dbconn.as_burn_state_db(),
+                burn_header_height,
+            )?;
 
         debug!(
             "Setup block: Processed epoch transition";
diff --git a/stackslib/src/chainstate/stacks/db/blocks.rs b/stackslib/src/chainstate/stacks/db/blocks.rs
index 233a9d5978..5f6b236973 100644
--- a/stackslib/src/chainstate/stacks/db/blocks.rs
+++ b/stackslib/src/chainstate/stacks/db/blocks.rs
@@ -4044,6 +4044,7 @@ impl StacksChainState {
     /// Return (applied?, receipts)
     pub fn process_epoch_transition(
         clarity_tx: &mut ClarityTx,
+        burn_dbconn: &dyn BurnStateDB,
         chain_tip_burn_header_height: u32,
     ) -> Result<(bool, Vec<StacksTransactionReceipt>), Error> {
         // is this stacks block the first of a new epoch?
@@ -4104,14 +4105,29 @@ impl StacksChainState {
                         current_epoch = StacksEpochId::Epoch30;
                     }
                     StacksEpochId::Epoch30 => {
-                        // no special initialization is needed, since only the coinbase emission
-                        // schedule is changing.
+                        receipts.append(&mut clarity_tx.block.initialize_epoch_3_1()?);
                         current_epoch = StacksEpochId::Epoch31;
                     }
                     StacksEpochId::Epoch31 => {
                         panic!("No defined transition from Epoch31 forward")
                     }
                 }
+
+                if current_epoch > StacksEpochId::Epoch2_05 {
+                    // clarity tx should now have the current epoch
+                    assert_eq!(
+                        clarity_tx.block.get_epoch(),
+                        current_epoch,
+                        "FATAL: clarity_tx does not have the current epoch"
+                    );
+
+                    // clarity DB should now have the current epoch
+                    assert_eq!(
+                        clarity_tx.block.get_clarity_db_epoch_version(burn_dbconn)?,
+                        current_epoch,
+                        "FATAL: clarity DB does not report the current epoch"
+                    );
+                }
             }
         }
 
@@ -5198,7 +5214,11 @@ impl StacksChainState {
 
         // is this stacks block the first of a new epoch?
         let (applied_epoch_transition, mut tx_receipts) =
-            StacksChainState::process_epoch_transition(&mut clarity_tx, burn_tip_height)?;
+            StacksChainState::process_epoch_transition(
+                &mut clarity_tx,
+                burn_dbconn,
+                burn_tip_height,
+            )?;
 
         debug!(
             "Setup block: Processed epoch transition at {}/{}",
diff --git a/stackslib/src/clarity_vm/clarity.rs b/stackslib/src/clarity_vm/clarity.rs
index a5497cea24..ee8795cadd 100644
--- a/stackslib/src/clarity_vm/clarity.rs
+++ b/stackslib/src/clarity_vm/clarity.rs
@@ -226,6 +226,21 @@ impl<'a, 'b> ClarityBlockConnection<'a, 'b> {
             None => None,
         }
     }
+
+    /// Load the epoch ID from the clarity DB.
+    /// Used to sanity-check epoch transitions.
+    pub fn get_clarity_db_epoch_version(
+        &mut self,
+        burn_state_db: &dyn BurnStateDB,
+    ) -> Result<StacksEpochId, Error> {
+        let mut db = self.datastore.as_clarity_db(self.header_db, burn_state_db);
+        // NOTE: the begin/roll_back shouldn't be necessary with how this gets used in practice,
+        // but is put here defensively.
+        db.begin();
+        let result = db.get_clarity_epoch_version();
+        db.roll_back()?;
+        Ok(result?)
+    }
 }
 
 impl ClarityInstance {
@@ -1524,6 +1539,32 @@ impl<'a, 'b> ClarityBlockConnection<'a, 'b> {
         })
     }
 
+    pub fn initialize_epoch_3_1(&mut self) -> Result<Vec<StacksTransactionReceipt>, Error> {
+        // use the `using!` statement to ensure that the old cost_tracker is placed
+        //  back in all branches after initialization
+        using!(self.cost_track, "cost tracker", |old_cost_tracker| {
+            // epoch initialization is *free*.
+            // NOTE: this also means that cost functions won't be evaluated.
+            self.cost_track.replace(LimitedCostTracker::new_free());
+            self.epoch = StacksEpochId::Epoch31;
+            self.as_transaction(|tx_conn| {
+                // bump the epoch in the Clarity DB
+                tx_conn
+                    .with_clarity_db(|db| {
+                        db.set_clarity_epoch_version(StacksEpochId::Epoch31)?;
+                        Ok(())
+                    })
+                    .unwrap();
+
+                // require 3.1 rules henceforth in this connection as well
+                tx_conn.epoch = StacksEpochId::Epoch31;
+            });
+
+            debug!("Epoch 3.1 initialized");
+            (old_cost_tracker, Ok(vec![]))
+        })
+    }
+
     pub fn start_transaction_processing<'c>(&'c mut self) -> ClarityTransactionConnection<'c, 'a> {
         let store = &mut self.datastore;
         let cost_track = &mut self.cost_track;
diff --git a/stackslib/src/core/mod.rs b/stackslib/src/core/mod.rs
index ba4dbf14d2..0f43c40756 100644
--- a/stackslib/src/core/mod.rs
+++ b/stackslib/src/core/mod.rs
@@ -496,7 +496,10 @@ pub static STACKS_EPOCH_3_0_MARKER: u8 = 0x0b;
 
 /// Stacks 3.1 epoch marker.  All block-commits in 3.1 must have a memo bitfield with this value
 /// *or greater*.
-pub static STACKS_EPOCH_3_1_MARKER: u8 = 0x0c;
+/// NOTE: it has to be 0x0d because a prior release of 3.1 with 0x0c before activation had a
+/// consensus bug. This forces miners with this buggy release off the network if they are still
+/// running it prior to 3.1 activation.
+pub static STACKS_EPOCH_3_1_MARKER: u8 = 0x0d;
 
 #[test]
 fn test_ord_for_stacks_epoch() {