diff --git a/.changelog/9428.txt b/.changelog/9428.txt
new file mode 100644
index 000000000000..5405590fc26f
--- /dev/null
+++ b/.changelog/9428.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+connect: connect CA Roots in the primary datacenter should use a SigningKeyID derived from their local intermediate
+```
diff --git a/GNUmakefile b/GNUmakefile
index 3253280e2c36..5bfb47ee18eb 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -359,10 +359,14 @@ ifeq ("$(CIRCLECI)","true")
 	gotestsum --format=short-verbose --junitfile "$(TEST_RESULTS_DIR)/gotestsum-report.xml" -- -cover -coverprofile=coverage.txt ./agent/connect/ca
 # Run leader tests that require Vault
 	gotestsum --format=short-verbose --junitfile "$(TEST_RESULTS_DIR)/gotestsum-report-leader.xml" -- -cover -coverprofile=coverage-leader.txt -run TestLeader_Vault_ ./agent/consul
+# Run agent tests that require Vault
+	gotestsum --format=short-verbose --junitfile "$(TEST_RESULTS_DIR)/gotestsum-report-agent.xml" -- -cover -coverprofile=coverage-agent.txt -run '.*_Vault_' ./agent
 else
 # Run locally
 	@echo "Running /agent/connect/ca tests in verbose mode"
 	@go test -v ./agent/connect/ca
+	@go test -v ./agent/consul -run 'TestLeader_Vault_'
+	@go test -v ./agent -run '.*_Vault_'
 endif
 
 proto: $(PROTOGOFILES) $(PROTOGOBINFILES)
diff --git a/agent/agent_endpoint_test.go b/agent/agent_endpoint_test.go
index bd251ee5fce6..85ab5291a4dc 100644
--- a/agent/agent_endpoint_test.go
+++ b/agent/agent_endpoint_test.go
@@ -21,6 +21,7 @@ import (
 	"github.com/hashicorp/consul/acl"
 	"github.com/hashicorp/consul/agent/config"
 	"github.com/hashicorp/consul/agent/connect"
+	"github.com/hashicorp/consul/agent/connect/ca"
 	"github.com/hashicorp/consul/agent/debug"
 	"github.com/hashicorp/consul/agent/local"
 	"github.com/hashicorp/consul/agent/structs"
@@ -5446,6 +5447,131 @@ func TestAgentConnectCALeafCert_goodNotLocal(t *testing.T) {
 	}
 }
 
+func TestAgentConnectCALeafCert_Vault_doesNotChurnLeafCertsAtIdle(t *testing.T) {
+	ca.SkipIfVaultNotPresent(t)
+
+	if testing.Short() {
+		t.Skip("too slow for testing.Short")
+	}
+
+	t.Parallel()
+
+	testVault := ca.NewTestVaultServer(t)
+	defer testVault.Stop()
+
+	assert := assert.New(t)
+	require := require.New(t)
+	a := StartTestAgent(t, TestAgent{Overrides: fmt.Sprintf(`
+		connect {
+			test_ca_leaf_root_change_spread = "1ns"
+			ca_provider = "vault"
+			ca_config {
+				address = %[1]q
+				token = %[2]q
+				root_pki_path = "pki-root/"
+				intermediate_pki_path = "pki-intermediate/"
+			}
+		}
+	`, testVault.Addr, testVault.RootToken)})
+	defer a.Shutdown()
+	testrpc.WaitForTestAgent(t, a.RPC, "dc1")
+	testrpc.WaitForActiveCARoot(t, a.RPC, "dc1", nil)
+
+	var ca1 *structs.CARoot
+	{
+		args := &structs.DCSpecificRequest{Datacenter: "dc1"}
+		var reply structs.IndexedCARoots
+		require.NoError(a.RPC("ConnectCA.Roots", args, &reply))
+		for _, r := range reply.Roots {
+			if r.ID == reply.ActiveRootID {
+				ca1 = r
+				break
+			}
+		}
+		require.NotNil(ca1)
+	}
+
+	{
+		// Register a local service
+		args := &structs.ServiceDefinition{
+			ID:      "foo",
+			Name:    "test",
+			Address: "127.0.0.1",
+			Port:    8000,
+			Check: structs.CheckType{
+				TTL: 15 * time.Second,
+			},
+		}
+		req, _ := http.NewRequest("PUT", "/v1/agent/service/register", jsonReader(args))
+		resp := httptest.NewRecorder()
+		_, err := a.srv.AgentRegisterService(resp, req)
+		require.NoError(err)
+		if !assert.Equal(200, resp.Code) {
+			t.Log("Body: ", resp.Body.String())
+		}
+	}
+
+	// List
+	req, _ := http.NewRequest("GET", "/v1/agent/connect/ca/leaf/test", nil)
+	resp := httptest.NewRecorder()
+	obj, err := a.srv.AgentConnectCALeafCert(resp, req)
+	require.NoError(err)
+	require.Equal("MISS", resp.Header().Get("X-Cache"))
+
+	// Get the issued cert
+	issued, ok := obj.(*structs.IssuedCert)
+	assert.True(ok)
+
+	// Verify that the cert is signed by the CA
+	requireLeafValidUnderCA(t, issued, ca1)
+
+	// Verify blocking index
+	assert.True(issued.ModifyIndex > 0)
+	assert.Equal(fmt.Sprintf("%d", issued.ModifyIndex),
+		resp.Header().Get("X-Consul-Index"))
+
+	// Test caching
+	{
+		// Fetch it again
+		resp := httptest.NewRecorder()
+		obj2, err := a.srv.AgentConnectCALeafCert(resp, req)
+		require.NoError(err)
+		require.Equal(obj, obj2)
+
+		// Should cache hit this time and not make request
+		require.Equal("HIT", resp.Header().Get("X-Cache"))
+	}
+
+	// Test that we aren't churning leaves for no reason at idle.
+	{
+		ch := make(chan error, 1)
+		go func() {
+			req, _ := http.NewRequest("GET", "/v1/agent/connect/ca/leaf/test?index="+strconv.Itoa(int(issued.ModifyIndex)), nil)
+			resp := httptest.NewRecorder()
+			obj, err := a.srv.AgentConnectCALeafCert(resp, req)
+			if err != nil {
+				ch <- err
+			} else {
+				issued2 := obj.(*structs.IssuedCert)
+				if issued.CertPEM == issued2.CertPEM {
+					ch <- fmt.Errorf("leaf woke up unexpectedly with same cert")
+				} else {
+					ch <- fmt.Errorf("leaf woke up unexpectedly with new cert")
+				}
+			}
+		}()
+
+		start := time.Now()
+
+		select {
+		case <-time.After(5 * time.Second):
+		case err := <-ch:
+			dur := time.Since(start)
+			t.Fatalf("unexpected return from blocking query; leaf churned during idle period, took %s: %v", dur, err)
+		}
+	}
+}
+
 func TestAgentConnectCALeafCert_secondaryDC_good(t *testing.T) {
 	t.Parallel()
 
diff --git a/agent/consul/leader_connect_ca.go b/agent/consul/leader_connect_ca.go
index ff30d50df141..d7bcd4222159 100644
--- a/agent/consul/leader_connect_ca.go
+++ b/agent/consul/leader_connect_ca.go
@@ -416,7 +416,7 @@ func (c *CAManager) initializeRootCA(provider ca.Provider, conf *structs.CAConfi
 	if err != nil {
 		return fmt.Errorf("error generating intermediate cert: %v", err)
 	}
-	_, err = connect.ParseCert(interPEM)
+	intermediateCert, err := connect.ParseCert(interPEM)
 	if err != nil {
 		return fmt.Errorf("error getting intermediate cert: %v", err)
 	}
@@ -439,6 +439,13 @@ func (c *CAManager) initializeRootCA(provider ca.Provider, conf *structs.CAConfi
 		}
 	}
 
+	// Versions prior to 1.9.3, 1.8.8, and 1.7.12 incorrectly used the primary
+	// rootCA's subjectKeyID here instead of the intermediate. For
+	// provider=consul this didn't matter since there are no intermediates in
+	// the primaryDC, but for vault it does matter.
+	expectedSigningKeyID := connect.EncodeSigningKeyID(intermediateCert.SubjectKeyId)
+	needsSigningKeyUpdate := (rootCA.SigningKeyID != expectedSigningKeyID)
+
 	// Check if the CA root is already initialized and exit if it is,
 	// adding on any existing intermediate certs since they aren't directly
 	// tied to the provider.
@@ -449,7 +456,10 @@ func (c *CAManager) initializeRootCA(provider ca.Provider, conf *structs.CAConfi
 	if err != nil {
 		return err
 	}
-	if activeRoot != nil {
+	if activeRoot != nil && needsSigningKeyUpdate {
+		c.logger.Info("Correcting stored SigningKeyID value", "previous", rootCA.SigningKeyID, "updated", expectedSigningKeyID)
+
+	} else if activeRoot != nil && !needsSigningKeyUpdate {
 		// This state shouldn't be possible to get into because we update the root and
 		// CA config in the same FSM operation.
 		if activeRoot.ID != rootCA.ID {
@@ -462,6 +472,10 @@ func (c *CAManager) initializeRootCA(provider ca.Provider, conf *structs.CAConfi
 		return nil
 	}
 
+	if needsSigningKeyUpdate {
+		rootCA.SigningKeyID = expectedSigningKeyID
+	}
+
 	// Get the highest index
 	idx, _, err := state.CARoots(nil)
 	if err != nil {
diff --git a/agent/consul/leader_connect_test.go b/agent/consul/leader_connect_test.go
index cf09b8c6b6d0..5fef3992262d 100644
--- a/agent/consul/leader_connect_test.go
+++ b/agent/consul/leader_connect_test.go
@@ -566,6 +566,111 @@ func TestLeader_SecondaryCA_IntermediateRefresh(t *testing.T) {
 	require.NoError(err)
 }
 
+func TestLeader_Vault_PrimaryCA_FixSigningKeyID_OnRestart(t *testing.T) {
+	ca.SkipIfVaultNotPresent(t)
+
+	if testing.Short() {
+		t.Skip("too slow for testing.Short")
+	}
+
+	t.Parallel()
+
+	testVault := ca.NewTestVaultServer(t)
+	defer testVault.Stop()
+
+	dir1pre, s1pre := testServerWithConfig(t, func(c *Config) {
+		c.Build = "1.6.0"
+		c.PrimaryDatacenter = "dc1"
+		c.CAConfig = &structs.CAConfiguration{
+			Provider: "vault",
+			Config: map[string]interface{}{
+				"Address":             testVault.Addr,
+				"Token":               testVault.RootToken,
+				"RootPKIPath":         "pki-root/",
+				"IntermediatePKIPath": "pki-intermediate/",
+			},
+		}
+	})
+	defer os.RemoveAll(dir1pre)
+	defer s1pre.Shutdown()
+
+	testrpc.WaitForLeader(t, s1pre.RPC, "dc1")
+
+	// Restore the pre-1.9.3/1.8.8/1.7.12 behavior of the SigningKeyID not being derived
+	// from the intermediates in the primary (which only matters for provider=vault).
+	var primaryRootSigningKeyID string
+	{
+		state := s1pre.fsm.State()
+
+		// Get the highest index
+		idx, activePrimaryRoot, err := state.CARootActive(nil)
+		require.NoError(t, err)
+		require.NotNil(t, activePrimaryRoot)
+
+		rootCert, err := connect.ParseCert(activePrimaryRoot.RootCert)
+		require.NoError(t, err)
+
+		// Force this to be derived just from the root, not the intermediate.
+		primaryRootSigningKeyID = connect.EncodeSigningKeyID(rootCert.SubjectKeyId)
+		activePrimaryRoot.SigningKeyID = primaryRootSigningKeyID
+
+		// Store the root cert in raft
+		resp, err := s1pre.raftApply(structs.ConnectCARequestType, &structs.CARequest{
+			Op:    structs.CAOpSetRoots,
+			Index: idx,
+			Roots: []*structs.CARoot{activePrimaryRoot},
+		})
+		require.NoError(t, err)
+		if respErr, ok := resp.(error); ok {
+			t.Fatalf("respErr: %v", respErr)
+		}
+	}
+
+	// Shutdown s1pre and restart it to trigger the secondary CA init to correct
+	// the SigningKeyID.
+	s1pre.Shutdown()
+
+	dir1, s1 := testServerWithConfig(t, func(c *Config) {
+		c.DataDir = s1pre.config.DataDir
+		c.Datacenter = "dc1"
+		c.PrimaryDatacenter = "dc1"
+		c.NodeName = s1pre.config.NodeName
+		c.NodeID = s1pre.config.NodeID
+	})
+	defer os.RemoveAll(dir1)
+	defer s1.Shutdown()
+
+	testrpc.WaitForLeader(t, s1.RPC, "dc1")
+
+	// Retry since it will take some time to init the primary CA fully and there
+	// isn't a super clean way to watch specifically until it's done than polling
+	// the CA provider anyway.
+	retry.Run(t, func(r *retry.R) {
+		// verify that the root is now corrected
+		provider, activeRoot := getCAProviderWithLock(s1)
+		require.NotNil(r, provider)
+		require.NotNil(r, activeRoot)
+
+		activeIntermediate, err := provider.ActiveIntermediate()
+		require.NoError(r, err)
+
+		intermediateCert, err := connect.ParseCert(activeIntermediate)
+		require.NoError(r, err)
+
+		// Force this to be derived just from the root, not the intermediate.
+		expect := connect.EncodeSigningKeyID(intermediateCert.SubjectKeyId)
+
+		// The in-memory representation was saw the correction via a setCAProvider call.
+		require.Equal(r, expect, activeRoot.SigningKeyID)
+
+		// The state store saw the correction, too.
+		_, activePrimaryRoot, err := s1.fsm.State().CARootActive(nil)
+		require.NoError(r, err)
+		require.NotNil(r, activePrimaryRoot)
+		require.Equal(r, expect, activePrimaryRoot.SigningKeyID)
+	})
+}
+
 func TestLeader_SecondaryCA_FixSigningKeyID_via_IntermediateRefresh(t *testing.T) {
 	t.Parallel()