diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index 30acc8224ec..2b6f43c45c2 100644
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -1653,7 +1653,7 @@ impl<SP: Deref> InteractivelyFunded<SP> for InboundV2Channel<SP> where SP::Targe
 	}
 }
 
-impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
+impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
 	fn new_for_inbound_channel<'a, ES: Deref, F: Deref, L: Deref>(
 		fee_estimator: &'a LowerBoundedFeeEstimator<F>,
 		entropy_source: &'a ES,
@@ -3747,6 +3747,15 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 		self.channel_transaction_parameters.channel_type_features = self.channel_type.clone();
 		Ok(())
 	}
+
+	/// Panics if the commitment tx numbers have advanced from their initial number.
+	fn assert_no_commitment_advancement(&self) {
+		if self.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
+				self.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
+				self.holder_commitment_point.transaction_number() != INITIAL_COMMITMENT_NUMBER {
+			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
+		}
+	}
 }
 
 // Internal utility functions for channels
@@ -4679,11 +4688,7 @@ impl<SP: Deref> Channel<SP> where
 					ClosureReason::HolderForceClosed { broadcasted_latest_txn: Some(false) },
 				)));
 		}
-		if self.context.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
-				self.context.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
-				self.context.holder_commitment_point.transaction_number() != INITIAL_COMMITMENT_NUMBER {
-			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
-		}
+		self.context.assert_no_commitment_advancement();
 
 		let funding_script = self.context.get_funding_redeemscript();
 
@@ -7987,11 +7992,7 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 		) {
 			panic!("Tried to get a funding_created messsage at a time other than immediately after initial handshake completion (or tried to get funding_created twice)");
 		}
-		if self.context.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
-				self.context.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
-				self.context.holder_commitment_point.transaction_number() != INITIAL_COMMITMENT_NUMBER {
-			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
-		}
+		self.context.assert_no_commitment_advancement();
 
 		self.context.channel_transaction_parameters.funding_outpoint = Some(funding_txo);
 		self.context.holder_signer.as_mut().provide_channel_parameters(&self.context.channel_transaction_parameters);
@@ -8115,11 +8116,7 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 		if !matches!(self.context.channel_state, ChannelState::FundingNegotiated) {
 			return Err((self, ChannelError::close("Received funding_signed in strange state!".to_owned())));
 		}
-		if self.context.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
-				self.context.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
-				self.context.holder_commitment_point.transaction_number() != INITIAL_COMMITMENT_NUMBER {
-			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
-		}
+		self.context.assert_no_commitment_advancement();
 
 		let funding_script = self.context.get_funding_redeemscript();
 
@@ -8411,11 +8408,7 @@ impl<SP: Deref> InboundV1Channel<SP> where SP::Target: SignerProvider {
 			// channel.
 			return Err((self, ChannelError::close("Received funding_created after we got the channel!".to_owned())));
 		}
-		if self.context.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
-				self.context.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
-				self.context.holder_commitment_point.transaction_number() != INITIAL_COMMITMENT_NUMBER {
-			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
-		}
+		self.context.assert_no_commitment_advancement();
 
 		let funding_txo = OutPoint { txid: msg.funding_txid, index: msg.funding_output_index };
 		self.context.channel_transaction_parameters.funding_outpoint = Some(funding_txo);