diff --git a/README.md b/README.md
index 18beace6c..bece11c0d 100644
--- a/README.md
+++ b/README.md
@@ -178,3 +178,8 @@ Development instructions for the CircleCI CLI can be found in [HACKING.md](HACKI
 
 Please see the [documentation](https://circleci-public.github.io/circleci-cli) or `circleci help` for more.
 
+## Server compatibility
+
+There are some difference of behavior depending on the version you use:
+ - config validation will use the GraphQL API until **Server v4.0.5, v4.1.3, v4.2.0**. The above versions will use the new route `compile-config-with-defaults`
+ - `circleci orb validate` will only allow you to validate orbs using other private orbs with the option `--org-slug` from version **Server v4.2.0**
diff --git a/api/api.go b/api/api.go
index 3d283930c..0c51b486d 100644
--- a/api/api.go
+++ b/api/api.go
@@ -564,7 +564,7 @@ func makeOrbRequest(cl *graphql.Client, configContent string, ownerId string) (*
 	}
 
 	if ownerId != "" {
-		return nil, errors.Errorf("Your version of server does not support validating orbs that refer private orbs")
+		return nil, errors.Errorf("Your version of Server does not support validating orbs that refer to other private orbs. Please see the README for more information on server compatibility: https://github.com/CircleCI-Public/circleci-cli#server-compatibility")
 	}
 	query := `
 		query ValidateOrb ($config: String!) {
diff --git a/cmd/orb_test.go b/cmd/orb_test.go
index 3d2f586d5..7b4e917ba 100644
--- a/cmd/orb_test.go
+++ b/cmd/orb_test.go
@@ -210,6 +210,77 @@ See a full explanation and documentation on orbs here: https://circleci.com/docs
 			})
 		})
 
+		Describe("with old server version", func() {
+			BeforeEach(func() {
+				token = "testtoken"
+				command = exec.Command(pathCLI,
+					"orb", "validate",
+					"--skip-update-check",
+					"--token", token,
+					"--host", tempSettings.TestServer.URL(),
+					"-",
+				)
+				stdin, err := command.StdinPipe()
+				Expect(err).ToNot(HaveOccurred())
+				go func() {
+					defer stdin.Close()
+					_, err := io.WriteString(stdin, "{}")
+					if err != nil {
+						panic(err)
+					}
+				}()
+			})
+
+			It("should use the old GraphQL resolver", func() {
+				By("setting up a mock server")
+
+				mockOrbIntrospection(false, "", tempSettings)
+
+				gqlResponse := `{
+							"orbConfig": {
+								"sourceYaml": "{}",
+								"valid": true,
+								"errors": []
+							}
+						}`
+
+				response := struct {
+					Query     string `json:"query"`
+					Variables struct {
+						Config string `json:"config"`
+					} `json:"variables"`
+				}{
+					Query: `
+		query ValidateOrb ($config: String!) {
+			orbConfig(orbYaml: $config) {
+				valid,
+				errors { message },
+				sourceYaml,
+				outputYaml
+			}
+		}`,
+					Variables: struct {
+						Config string `json:"config"`
+					}{
+						Config: "{}",
+					},
+				}
+				expected, err := json.Marshal(response)
+				Expect(err).ShouldNot(HaveOccurred())
+
+				tempSettings.AppendPostHandler(token, clitest.MockRequestResponse{
+					Status:   http.StatusOK,
+					Request:  string(expected),
+					Response: gqlResponse})
+
+				session, err := gexec.Start(command, GinkgoWriter, GinkgoWriter)
+
+				Expect(err).ShouldNot(HaveOccurred())
+				Eventually(session.Out).Should(gbytes.Say("Orb input is valid."))
+				Eventually(session).Should(gexec.Exit(0))
+			})
+		})
+
 		Context("with 'some orb'", func() {
 			BeforeEach(func() {
 				orb.Write([]byte(`some orb`))