diff --git a/src/common/models/project.go b/src/common/models/project.go
index c89b0aba5..3bf34a7a5 100644
--- a/src/common/models/project.go
+++ b/src/common/models/project.go
@@ -80,6 +80,11 @@ func (p *Project) IsPublic() bool {
 	return isTrue(public)
 }
 
+// IsProxy returns true when the project type is proxy cache
+func (p *Project) IsProxy() bool {
+	return p.RegistryID > 0
+}
+
 // ContentTrustEnabled ...
 func (p *Project) ContentTrustEnabled() bool {
 	enabled, exist := p.GetMetadata(ProMetaEnableContentTrust)
diff --git a/src/server/middleware/repoproxy/proxy.go b/src/server/middleware/repoproxy/proxy.go
index f147d58d5..dc7266d7d 100644
--- a/src/server/middleware/repoproxy/proxy.go
+++ b/src/server/middleware/repoproxy/proxy.go
@@ -17,20 +17,20 @@ package repoproxy
 import (
 	"context"
 	"fmt"
-	"github.com/goharbor/harbor/src/common/security"
-	"github.com/goharbor/harbor/src/common/security/proxycachesecret"
-	"github.com/goharbor/harbor/src/lib/errors"
-	httpLib "github.com/goharbor/harbor/src/lib/http"
-	"github.com/goharbor/harbor/src/replication/model"
-	"github.com/goharbor/harbor/src/replication/registry"
 	"io"
 	"net/http"
 
 	"github.com/goharbor/harbor/src/common/models"
+	"github.com/goharbor/harbor/src/common/security"
+	"github.com/goharbor/harbor/src/common/security/proxycachesecret"
 	"github.com/goharbor/harbor/src/controller/project"
 	"github.com/goharbor/harbor/src/controller/proxy"
 	"github.com/goharbor/harbor/src/lib"
+	"github.com/goharbor/harbor/src/lib/errors"
+	httpLib "github.com/goharbor/harbor/src/lib/http"
 	"github.com/goharbor/harbor/src/lib/log"
+	"github.com/goharbor/harbor/src/replication/model"
+	"github.com/goharbor/harbor/src/replication/registry"
 	"github.com/goharbor/harbor/src/server/middleware"
 )
 
@@ -163,14 +163,6 @@ func setHeaders(w http.ResponseWriter, size int64, mediaType string, dig string)
 	h.Set("Etag", dig)
 }
 
-// isProxyProject check the project is a proxy project
-func isProxyProject(p *models.Project) bool {
-	if p == nil {
-		return false
-	}
-	return p.RegistryID > 0
-}
-
 // isProxySession check if current security context is proxy session
 func isProxySession(ctx context.Context) bool {
 	sc, ok := security.FromContext(ctx)
@@ -194,7 +186,7 @@ func DisableBlobAndManifestUploadMiddleware() func(http.Handler) http.Handler {
 			httpLib.SendError(w, err)
 			return
 		}
-		if isProxyProject(p) && !isProxySession(ctx) {
+		if p.IsProxy() && !isProxySession(ctx) {
 			httpLib.SendError(w,
 				errors.DeniedError(
 					errors.Errorf("can not push artifact to a proxy project: %v", p.Name)))
diff --git a/src/server/middleware/repoproxy/proxy_test.go b/src/server/middleware/repoproxy/proxy_test.go
index e75b79012..7c83d7669 100644
--- a/src/server/middleware/repoproxy/proxy_test.go
+++ b/src/server/middleware/repoproxy/proxy_test.go
@@ -18,44 +18,12 @@ import (
 	"context"
 	"testing"
 
-	"github.com/goharbor/harbor/src/common/models"
 	"github.com/goharbor/harbor/src/common/security"
 	"github.com/goharbor/harbor/src/common/security/proxycachesecret"
 	securitySecret "github.com/goharbor/harbor/src/common/security/secret"
 	"github.com/goharbor/harbor/src/core/config"
 )
 
-func TestIsProxyProject(t *testing.T) {
-	cases := []struct {
-		name string
-		in   *models.Project
-		want bool
-	}{
-		{
-			name: `no proxy`,
-			in:   &models.Project{RegistryID: 0},
-			want: false,
-		},
-		{
-			name: `normal proxy`,
-			in:   &models.Project{RegistryID: 1},
-			want: true,
-		},
-	}
-
-	for _, tt := range cases {
-		t.Run(tt.name, func(t *testing.T) {
-
-			got := isProxyProject(tt.in)
-
-			if got != tt.want {
-				t.Errorf(`(%v) = %v; want "%v"`, tt.in, got, tt.want)
-			}
-
-		})
-	}
-}
-
 func TestIsProxySession(t *testing.T) {
 	config.Init()
 	sc1 := securitySecret.NewSecurityContext("123456789", config.SecretStore)
diff --git a/src/server/v2.0/handler/artifact.go b/src/server/v2.0/handler/artifact.go
index 53a56f279..265b5d528 100644
--- a/src/server/v2.0/handler/artifact.go
+++ b/src/server/v2.0/handler/artifact.go
@@ -17,9 +17,6 @@ package handler
 import (
 	"context"
 	"fmt"
-	"github.com/goharbor/harbor/src/controller/event/metadata"
-	"github.com/goharbor/harbor/src/controller/project"
-	"github.com/goharbor/harbor/src/pkg/notification"
 	"net/http"
 	"strings"
 	"time"
@@ -31,10 +28,13 @@ import (
 	"github.com/goharbor/harbor/src/common/utils"
 	"github.com/goharbor/harbor/src/controller/artifact"
 	"github.com/goharbor/harbor/src/controller/artifact/processor"
+	"github.com/goharbor/harbor/src/controller/event/metadata"
+	"github.com/goharbor/harbor/src/controller/project"
 	"github.com/goharbor/harbor/src/controller/repository"
 	"github.com/goharbor/harbor/src/controller/scan"
 	"github.com/goharbor/harbor/src/controller/tag"
 	"github.com/goharbor/harbor/src/lib/errors"
+	"github.com/goharbor/harbor/src/pkg/notification"
 	"github.com/goharbor/harbor/src/server/v2.0/handler/assembler"
 	"github.com/goharbor/harbor/src/server/v2.0/handler/model"
 	"github.com/goharbor/harbor/src/server/v2.0/models"
@@ -244,7 +244,7 @@ func (a *artifactAPI) requireNonProxyCacheProject(ctx context.Context, name stri
 	if err != nil {
 		return err
 	}
-	if pro.RegistryID > 0 {
+	if pro.IsProxy() {
 		return errors.New(nil).WithCode(errors.MethodNotAllowedCode).
 			WithMessage("the operation isn't supported for a proxy cache project")
 	}
diff --git a/src/server/v2.0/handler/project.go b/src/server/v2.0/handler/project.go
index c8c1dc258..ee6aae8c7 100644
--- a/src/server/v2.0/handler/project.go
+++ b/src/server/v2.0/handler/project.go
@@ -3,7 +3,6 @@ package handler
 import (
 	"context"
 	"fmt"
-	"github.com/goharbor/harbor/src/pkg/robot"
 	"strconv"
 	"strings"
 	"sync"
@@ -29,6 +28,7 @@ import (
 	"github.com/goharbor/harbor/src/pkg/project/metadata"
 	"github.com/goharbor/harbor/src/pkg/quota/types"
 	"github.com/goharbor/harbor/src/pkg/retention/policy"
+	"github.com/goharbor/harbor/src/pkg/robot"
 	"github.com/goharbor/harbor/src/pkg/user"
 	"github.com/goharbor/harbor/src/replication"
 	"github.com/goharbor/harbor/src/server/v2.0/handler/model"
@@ -116,6 +116,12 @@ func (a *projectAPI) CreateProject(ctx context.Context, params operation.CreateP
 		req.Metadata.Public = strconv.FormatBool(false)
 	}
 
+	// ignore enable_content_trust metadata for proxy cache project
+	// see https://github.com/goharbor/harbor/issues/12940 to get more info
+	if req.RegistryID != nil {
+		req.Metadata.EnableContentTrust = nil
+	}
+
 	// validate the RegistryID and StorageLimit in the body of the request
 	if err := a.validateProjectReq(ctx, req); err != nil {
 		return a.SendError(ctx, err)
@@ -306,7 +312,7 @@ func (a *projectAPI) GetProjectSummary(ctx context.Context, params operation.Get
 		fetchSummaries = append(fetchSummaries, getProjectMemberSummary)
 	}
 
-	if p.RegistryID > 0 {
+	if p.IsProxy() {
 		fetchSummaries = append(fetchSummaries, getProjectRegistrySummary)
 	}
 
@@ -450,6 +456,11 @@ func (a *projectAPI) UpdateProject(ctx context.Context, params operation.UpdateP
 		}
 	}
 
+	// ignore enable_content_trust metadata for proxy cache project
+	// see https://github.com/goharbor/harbor/issues/12940 to get more info
+	if params.Project.Metadata != nil && p.IsProxy() {
+		params.Project.Metadata.EnableContentTrust = nil
+	}
 	lib.JSONCopy(&p.Metadata, params.Project.Metadata)
 
 	if err := a.projectCtl.Update(ctx, p); err != nil {