diff --git a/rhp/v4/rhp.go b/rhp/v4/rhp.go
index 176851e..478a911 100644
--- a/rhp/v4/rhp.go
+++ b/rhp/v4/rhp.go
@@ -12,7 +12,9 @@ import (
 )
 
 const (
-	proofWindow = 144 // 24 hours
+	// ProofWindow is the number of blocks a host has to submit a proof after
+	// the contract expires.
+	ProofWindow = 144 // 24 hours
 
 	// SectorSize is the size of one sector in bytes.
 	SectorSize = 1 << 22 // 4 MiB
@@ -564,7 +566,7 @@ func NewContract(p HostPrices, cp RPCFormContractParams, hostKey types.PublicKey
 			Filesize:         0,
 			FileMerkleRoot:   types.Hash256{},
 			ProofHeight:      cp.ProofHeight,
-			ExpirationHeight: cp.ProofHeight + proofWindow,
+			ExpirationHeight: cp.ProofHeight + ProofWindow,
 			RenterOutput: types.SiacoinOutput{
 				Value:   cp.Allowance,
 				Address: cp.RenterAddress,
@@ -686,7 +688,7 @@ func RenewContract(fc types.V2FileContract, prices HostPrices, rp RPCRenewContra
 	renewal.NewContract.RevisionNumber = 0
 	renewal.NewContract.RenterSignature = types.Signature{}
 	renewal.NewContract.HostSignature = types.Signature{}
-	renewal.NewContract.ExpirationHeight = rp.ProofHeight + proofWindow
+	renewal.NewContract.ExpirationHeight = rp.ProofHeight + ProofWindow
 	renewal.NewContract.ProofHeight = rp.ProofHeight
 	// the renter output value only needs to cover the new allowance
 	renewal.NewContract.RenterOutput.Value = rp.Allowance
diff --git a/rhp/v4/validation.go b/rhp/v4/validation.go
index 41fcfcb..a36d781 100644
--- a/rhp/v4/validation.go
+++ b/rhp/v4/validation.go
@@ -35,14 +35,14 @@ func (req *RPCWriteSectorStreamingRequest) Validate(pk types.PublicKey, maxDurat
 	switch {
 	case req.Duration == 0:
 		return errors.New("duration must be greater than 0")
+	case req.Duration > maxDuration:
+		return fmt.Errorf("duration exceeds maximum: %d > %d", req.Duration, maxDuration)
 	case req.DataLength == 0:
 		return errors.New("sector must not be empty")
 	case req.DataLength%LeafSize != 0:
 		return errors.New("sector must be segment aligned")
 	case req.DataLength > SectorSize:
 		return errors.New("sector exceeds sector bounds")
-	case req.Duration > maxDuration:
-		return fmt.Errorf("duration exceeds maximum: %d > %d", req.Duration, maxDuration)
 	}
 	return nil
 }
@@ -103,7 +103,7 @@ func (req *RPCFormContractRequest) Validate(pk types.PublicKey, tip types.ChainI
 
 	// validate the contract fields
 	hp := req.Prices
-	expirationHeight := req.Contract.ProofHeight + proofWindow
+	expirationHeight := req.Contract.ProofHeight + ProofWindow
 	duration := expirationHeight - hp.TipHeight
 	// calculate the minimum allowance required for the contract based on the
 	// host's locked collateral and the contract duration
@@ -143,7 +143,7 @@ func (req *RPCRenewContractRequest) Validate(pk types.PublicKey, tip types.Chain
 
 	// validate the contract fields
 	hp := req.Prices
-	expirationHeight := req.Renewal.ProofHeight + proofWindow
+	expirationHeight := req.Renewal.ProofHeight + ProofWindow
 	duration := expirationHeight - hp.TipHeight
 	// calculate the minimum allowance required for the contract based on the
 	// host's locked collateral and the contract duration