diff --git a/controller/gateway/controller_reconciler_utils.go b/controller/gateway/controller_reconciler_utils.go
index 8551b7be1..2b2fabcc2 100644
--- a/controller/gateway/controller_reconciler_utils.go
+++ b/controller/gateway/controller_reconciler_utils.go
@@ -24,6 +24,7 @@ import (
 	gatewayv1beta1 "sigs.k8s.io/gateway-api/apis/v1beta1"
 
 	operatorv1beta1 "github.com/kong/gateway-operator/api/v1beta1"
+	"github.com/kong/gateway-operator/controller/pkg/secrets"
 	operatorerrors "github.com/kong/gateway-operator/internal/errors"
 	gwtypes "github.com/kong/gateway-operator/internal/types"
 	"github.com/kong/gateway-operator/internal/utils/gatewayclass"
@@ -875,10 +876,25 @@ func getSupportedKindsWithResolvedRefsCondition(ctx context.Context, c client.Cl
 				secretNamespace = string(*certificateRef.Namespace)
 			}
 
+			isReferenceGranted := true
+			// In case there is a cross-namespace reference, check if there is any referenceGrant allowing it.
+			if secretNamespace != gatewayNamespace {
+				referenceGrantList := &gatewayv1beta1.ReferenceGrantList{}
+				err = c.List(ctx, referenceGrantList, client.InNamespace(secretNamespace))
+				if err != nil {
+					return
+				}
+				if !isSecretCrossReferenceGranted(gatewayv1.Namespace(gatewayNamespace), certificateRef.Name, referenceGrantList.Items) {
+					resolvedRefsCondition.Reason = string(gatewayv1.ListenerReasonRefNotPermitted)
+					message = conditionMessage(message, fmt.Sprintf("Secret %s/%s reference not allowed by any referenceGrant", secretNamespace, certificateRef.Name))
+					isReferenceGranted = false
+				}
+			}
+
 			var secretExists bool
-			if isValidGroupKind {
+			certificateSecret := &corev1.Secret{}
+			if isValidGroupKind && isReferenceGranted {
 				// Get the secret and check it exists.
-				certificateSecret := &corev1.Secret{}
 				err = c.Get(ctx, types.NamespacedName{
 					Namespace: secretNamespace,
 					Name:      string(certificateRef.Name),
@@ -894,18 +910,11 @@ func getSupportedKindsWithResolvedRefsCondition(ctx context.Context, c client.Cl
 				}
 			}
 
-			if secretExists {
-				// In case there is a cross-namespace reference, check if there is any referenceGrant allowing it.
-				if secretNamespace != gatewayNamespace {
-					referenceGrantList := &gatewayv1beta1.ReferenceGrantList{}
-					err = c.List(ctx, referenceGrantList, client.InNamespace(secretNamespace))
-					if err != nil {
-						return
-					}
-					if !isSecretCrossReferenceGranted(gatewayv1.Namespace(gatewayNamespace), certificateRef.Name, referenceGrantList.Items) {
-						resolvedRefsCondition.Reason = string(gatewayv1.ListenerReasonRefNotPermitted)
-						message = conditionMessage(message, fmt.Sprintf("Secret %s/%s reference not allowed by any referenceGrant", secretNamespace, certificateRef.Name))
-					}
+			if isReferenceGranted && secretExists {
+				// Check if the secret is a valid TLS secret.
+				if !secrets.IsTLSSecretValid(certificateSecret) {
+					resolvedRefsCondition.Reason = string(gatewayv1.ListenerReasonInvalidCertificateRef)
+					message = conditionMessage(message, "Referenced secret does not contain a valid TLS certificate")
 				}
 			}
 		}
diff --git a/controller/pkg/secrets/cert.go b/controller/pkg/secrets/cert.go
index 120aaf236..32db56899 100644
--- a/controller/pkg/secrets/cert.go
+++ b/controller/pkg/secrets/cert.go
@@ -147,6 +147,25 @@ func signCertificate(csr certificatesv1.CertificateSigningRequest, ca *corev1.Se
 	return certBytes, nil
 }
 
+// IsTLSSecretValid checks if a Secret contains a valid TLS certificate and key.
+func IsTLSSecretValid(secret *corev1.Secret) bool {
+	var ok bool
+	var crt, key []byte
+	if crt, ok = secret.Data["tls.crt"]; !ok {
+		return false
+	}
+	if key, ok = secret.Data["tls.key"]; !ok {
+		return false
+	}
+	if p, _ := pem.Decode(crt); p == nil {
+		return false
+	}
+	if p, _ := pem.Decode(key); p == nil {
+		return false
+	}
+	return true
+}
+
 // EnsureCertificate creates a namespace/name Secret for subject signed by the CA in the
 // mtlsCASecretNamespace/mtlsCASecretName Secret, or does nothing if a namespace/name Secret is
 // already present. It returns a boolean indicating if it created a Secret and an error indicating
diff --git a/test/conformance/conformance_test.go b/test/conformance/conformance_test.go
index c0204630e..f283065c7 100644
--- a/test/conformance/conformance_test.go
+++ b/test/conformance/conformance_test.go
@@ -27,18 +27,12 @@ import (
 )
 
 var skippedTestsForExpressionsRouter = []string{
-	// gateway
-	tests.GatewayInvalidTLSConfiguration.ShortName,
-
 	// TODO: remove the skip https://github.com/Kong/gateway-operator/issues/295
 	// This test is flaky.
 	tests.HTTPRouteWeight.ShortName,
 }
 
 var skippedTestsForTraditionalCompatibleRouter = []string{
-	// gateway
-	tests.GatewayInvalidTLSConfiguration.ShortName,
-
 	// httproute
 	tests.HTTPRouteHeaderMatching.ShortName,
 	tests.HTTPRouteInvalidBackendRefUnknownKind.ShortName,