diff --git a/go.mod b/go.mod
index 9824f250..6b63819d 100644
--- a/go.mod
+++ b/go.mod
@@ -25,6 +25,6 @@ require (
 	golang.org/x/sync v0.6.0 // indirect
 )
 
-replace github.com/notaryproject/notation-core-go => github.com/Two-Hearts/notation-core-go v0.0.0-20240510081223-bf89fbfde06f
+replace github.com/notaryproject/notation-core-go => github.com/Two-Hearts/notation-core-go v0.0.0-20240604074342-99b519049ef9
 
-replace github.com/notaryproject/tspclient-go => github.com/Two-Hearts/tspclient-go v0.0.0-20240510080813-e58c4f362fa4
+replace github.com/notaryproject/tspclient-go => github.com/Two-Hearts/tspclient-go v0.0.0-20240604030442-e5d82db3a4d4
diff --git a/go.sum b/go.sum
index 9b41f8fb..c0ddc38a 100644
--- a/go.sum
+++ b/go.sum
@@ -1,9 +1,9 @@
 github.com/Azure/go-ntlmssp v0.0.0-20221128193559-754e69321358 h1:mFRzDkZVAjdal+s7s0MwaRv9igoPqLRdzOLzw/8Xvq8=
 github.com/Azure/go-ntlmssp v0.0.0-20221128193559-754e69321358/go.mod h1:chxPXzSsl7ZWRAuOIE23GDNzjWuZquvFlgA8xmpunjU=
-github.com/Two-Hearts/notation-core-go v0.0.0-20240510081223-bf89fbfde06f h1:0qJ4YyR0q7SYv9N1VMafb5823SpxI7AGuYnSlvEcTjo=
-github.com/Two-Hearts/notation-core-go v0.0.0-20240510081223-bf89fbfde06f/go.mod h1:KDiMLnM1MHQRMeiPM622MN0MBb9Hz6xRU4/O9qDOics=
-github.com/Two-Hearts/tspclient-go v0.0.0-20240510080813-e58c4f362fa4 h1:jtwluHassbSXeXjloQ5FCJJ1hOhN/DCnAztY8Cr6if0=
-github.com/Two-Hearts/tspclient-go v0.0.0-20240510080813-e58c4f362fa4/go.mod h1:LGyA/6Kwd2FlM0uk8Vc5il3j0CddbWSHBj/4kxQDbjs=
+github.com/Two-Hearts/notation-core-go v0.0.0-20240604074342-99b519049ef9 h1:gMwiXl+IGOeVhF4KUHbfqbvqZsgONcqPtzfYBexFKRE=
+github.com/Two-Hearts/notation-core-go v0.0.0-20240604074342-99b519049ef9/go.mod h1:uk5VrENYWqPdnnBOZCEk1XEfilOscHJckfhaWzuMJlU=
+github.com/Two-Hearts/tspclient-go v0.0.0-20240604030442-e5d82db3a4d4 h1:WCm4ObRL++IM3gVexV7evDbhzk2c4iAZYJmlTWIBOnQ=
+github.com/Two-Hearts/tspclient-go v0.0.0-20240604030442-e5d82db3a4d4/go.mod h1:LGyA/6Kwd2FlM0uk8Vc5il3j0CddbWSHBj/4kxQDbjs=
 github.com/alexbrainman/sspi v0.0.0-20231016080023-1a75b4708caa h1:LHTHcTQiSGT7VVbI0o4wBRNQIgn917usHWOd6VAffYI=
 github.com/alexbrainman/sspi v0.0.0-20231016080023-1a75b4708caa/go.mod h1:cEWa1LVoE5KvSD9ONXsZrj0z6KqySlCCNKHlLzbqAt4=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
diff --git a/verifier/helpers.go b/verifier/helpers.go
index 43ddb7ce..057239e1 100644
--- a/verifier/helpers.go
+++ b/verifier/helpers.go
@@ -168,3 +168,18 @@ func loadX509TrustStoresWithType(ctx context.Context, trustStoreType truststore.
 	}
 	return certificates, nil
 }
+
+// isTSATrustStoreInPolicy checks if tsa trust store is configured in
+// trust policy
+func isTSATrustStoreInPolicy(policy *trustpolicy.TrustPolicy) (bool, error) {
+	for _, trustStore := range policy.TrustStores {
+		storeType, _, found := strings.Cut(trustStore, ":")
+		if !found {
+			return false, truststore.TrustStoreError{Msg: fmt.Sprintf("invalid trust policy statement: %q is missing separator in trust store value %q. The required format is <TrustStoreType>:<TrustStoreName>", policy.Name, trustStore)}
+		}
+		if truststore.Type(storeType) == truststore.TypeTSA {
+			return true, nil
+		}
+	}
+	return false, nil
+}
diff --git a/verifier/verifier.go b/verifier/verifier.go
index 7192abad..996fdd2a 100644
--- a/verifier/verifier.go
+++ b/verifier/verifier.go
@@ -525,19 +525,19 @@ func verifyAuthenticTimestamp(ctx context.Context, trustPolicy *trustpolicy.Trus
 		timeStampLowerLimit := time.Now()
 		timeStampUpperLimit := timeStampLowerLimit
 		// check if tsa trust store is configured in trust policy
-		trustTSACerts, err := loadX509TSATrustStores(ctx, outcome.EnvelopeContent.SignerInfo.SignedAttributes.SigningScheme, trustPolicy, x509TrustStore)
+		tsaEnabled, err := isTSATrustStoreInPolicy(trustPolicy)
 		if err != nil {
 			return &notation.ValidationResult{
-				Error:  fmt.Errorf("failed to load tsa trust store with error: %w", err),
+				Error:  fmt.Errorf("failed to check tsa trust store configuration in turst policy with error: %w", err),
 				Type:   trustpolicy.TypeAuthenticTimestamp,
 				Action: outcome.VerificationLevel.Enforcement[trustpolicy.TypeAuthenticTimestamp],
 			}
 		}
-		if len(trustTSACerts) < 1 {
+		if !tsaEnabled {
 			performTimestampVerification = false
 		}
 		// check based on 'verifyTimestamp' field
-		if trustPolicy.SignatureVerification.VerifyTimestamp == trustpolicy.OptionAfterCertExpiry {
+		if performTimestampVerification && trustPolicy.SignatureVerification.VerifyTimestamp == trustpolicy.OptionAfterCertExpiry {
 			// check if signing cert chain has expired
 			var expired bool
 			for _, cert := range signerInfo.CertificateChain {
@@ -586,7 +586,7 @@ func verifyAuthenticTimestamp(ctx context.Context, trustPolicy *trustpolicy.Trus
 		}
 		// 2. Verify the timestamp countersignature
 		logger.Info("Verifying the timestamp countersignature...")
-		signedToken, err := tspclient.ParseSignedToken(ctx, signerInfo.UnsignedAttributes.TimestampSignature)
+		signedToken, err := tspclient.ParseSignedToken(signerInfo.UnsignedAttributes.TimestampSignature)
 		if err != nil {
 			return &notation.ValidationResult{
 				Error:  fmt.Errorf("failed to parse timestamp countersignature with error: %w", err),
@@ -611,6 +611,21 @@ func verifyAuthenticTimestamp(ctx context.Context, trustPolicy *trustpolicy.Trus
 			}
 		}
 		roots := x509.NewCertPool()
+		trustTSACerts, err := loadX509TSATrustStores(ctx, outcome.EnvelopeContent.SignerInfo.SignedAttributes.SigningScheme, trustPolicy, x509TrustStore)
+		if err != nil {
+			return &notation.ValidationResult{
+				Error:  fmt.Errorf("failed to load tsa trust store with error: %w", err),
+				Type:   trustpolicy.TypeAuthenticTimestamp,
+				Action: outcome.VerificationLevel.Enforcement[trustpolicy.TypeAuthenticTimestamp],
+			}
+		}
+		if len(trustTSACerts) < 1 {
+			return &notation.ValidationResult{
+				Error:  errors.New("no TSA root cert found in trust store"),
+				Type:   trustpolicy.TypeAuthenticTimestamp,
+				Action: outcome.VerificationLevel.Enforcement[trustpolicy.TypeAuthenticTimestamp],
+			}
+		}
 		for _, cert := range trustTSACerts {
 			roots.AddCert(cert)
 		}