diff --git a/.github/docs/openapi3.txt b/.github/docs/openapi3.txt
index 7c19ece4f..0ada195c8 100644
--- a/.github/docs/openapi3.txt
+++ b/.github/docs/openapi3.txt
@@ -55,8 +55,6 @@ var (
 	// ErrSchemaInputInf may be returned when validating a number
 	ErrSchemaInputInf = errors.New("floating point Inf is not allowed")
 )
-var CircularReferenceCounter = 3
-var CircularReferenceError = "kin-openapi bug found: circular schema reference not handled"
 var DefaultReadFromURI = URIMapCache(ReadFromURIs(ReadFromHTTP(http.DefaultClient), ReadFromFile))
     DefaultReadFromURI returns a caching ReadFromURIFunc which can read remote
     HTTP URIs and local file URIs.
diff --git a/README.md b/README.md
index cdf1f8570..d355d0ddd 100644
--- a/README.md
+++ b/README.md
@@ -303,6 +303,9 @@ for _, path := range doc.Paths.InMatchingOrder() {
 
 ## CHANGELOG: Sub-v1 breaking API changes
 
+### v0.126.0
+* `openapi3.CircularReferenceError` and `openapi3.CircularReferenceCounter` are removed. `openapi3.Loader` now implements reference backtracking, so any kind of circular references should be properly resolved.
+
 ### v0.125.0
 * The `openapi3filter.ErrFunc` and `openapi3filter.LogFunc` func types now take the validated request's context as first argument.
 
diff --git a/cmd/validate/main.go b/cmd/validate/main.go
index a0580967b..874f30c26 100644
--- a/cmd/validate/main.go
+++ b/cmd/validate/main.go
@@ -12,11 +12,6 @@ import (
 	"github.com/getkin/kin-openapi/openapi3"
 )
 
-var (
-	defaultCircular = openapi3.CircularReferenceCounter
-	circular        = flag.Int("circular", defaultCircular, "bump this (upper) limit when there's trouble with cyclic schema references")
-)
-
 var (
 	defaultDefaults = true
 	defaults        = flag.Bool("defaults", defaultDefaults, "when false, disables schemas' default field validation")
@@ -59,7 +54,6 @@ func main() {
 
 	switch {
 	case vd.OpenAPI == "3" || strings.HasPrefix(vd.OpenAPI, "3."):
-		openapi3.CircularReferenceCounter = *circular
 		loader := openapi3.NewLoader()
 		loader.IsExternalRefsAllowed = *ext
 
@@ -90,9 +84,6 @@ func main() {
 
 	case vd.OpenAPI == "2" || strings.HasPrefix(vd.OpenAPI, "2."),
 		vd.Swagger == "2" || strings.HasPrefix(vd.Swagger, "2."):
-		if *circular != defaultCircular {
-			log.Fatal("Flag --circular is only for OpenAPIv3")
-		}
 		if *defaults != defaultDefaults {
 			log.Fatal("Flag --defaults is only for OpenAPIv3")
 		}
diff --git a/openapi3/issue570_test.go b/openapi3/issue570_test.go
index 75afb7e3e..1575e5599 100644
--- a/openapi3/issue570_test.go
+++ b/openapi3/issue570_test.go
@@ -9,5 +9,5 @@ import (
 func TestIssue570(t *testing.T) {
 	loader := NewLoader()
 	_, err := loader.LoadFromFile("testdata/issue570.json")
-	require.ErrorContains(t, err, CircularReferenceError)
+	require.NoError(t, err)
 }
diff --git a/openapi3/issue615_test.go b/openapi3/issue615_test.go
index 67144e9e1..02532bb5a 100644
--- a/openapi3/issue615_test.go
+++ b/openapi3/issue615_test.go
@@ -9,21 +9,6 @@ import (
 )
 
 func TestIssue615(t *testing.T) {
-	{
-		var old int
-		old, openapi3.CircularReferenceCounter = openapi3.CircularReferenceCounter, 1
-		defer func() { openapi3.CircularReferenceCounter = old }()
-
-		loader := openapi3.NewLoader()
-		loader.IsExternalRefsAllowed = true
-		_, err := loader.LoadFromFile("testdata/recursiveRef/issue615.yml")
-		require.ErrorContains(t, err, openapi3.CircularReferenceError)
-	}
-
-	var old int
-	old, openapi3.CircularReferenceCounter = openapi3.CircularReferenceCounter, 4
-	defer func() { openapi3.CircularReferenceCounter = old }()
-
 	loader := openapi3.NewLoader()
 	loader.IsExternalRefsAllowed = true
 	doc, err := loader.LoadFromFile("testdata/recursiveRef/issue615.yml")
diff --git a/openapi3/issue796_test.go b/openapi3/issue796_test.go
index 0900ee5b9..9c8be17f2 100644
--- a/openapi3/issue796_test.go
+++ b/openapi3/issue796_test.go
@@ -7,11 +7,6 @@ import (
 )
 
 func TestIssue796(t *testing.T) {
-	var old int
-	// Need to set CircularReferenceCounter to > 10
-	old, CircularReferenceCounter = CircularReferenceCounter, 20
-	defer func() { CircularReferenceCounter = old }()
-
 	loader := NewLoader()
 	doc, err := loader.LoadFromFile("testdata/issue796.yml")
 	require.NoError(t, err)
diff --git a/openapi3/load_cicular_ref_with_external_file_test.go b/openapi3/load_cicular_ref_with_external_file_test.go
index 7a99e7600..cff5c01fe 100644
--- a/openapi3/load_cicular_ref_with_external_file_test.go
+++ b/openapi3/load_cicular_ref_with_external_file_test.go
@@ -47,6 +47,19 @@ func TestLoadCircularRefFromFile(t *testing.T) {
 	bar.Value.Properties["foo"] = &openapi3.SchemaRef{Ref: "#/components/schemas/Foo", Value: foo.Value}
 	foo.Value.Properties["bar"] = &openapi3.SchemaRef{Ref: "#/components/schemas/Bar", Value: bar.Value}
 
+	bazNestedRef := &openapi3.SchemaRef{Ref: "./baz.yml#/BazNested"}
+	array := openapi3.NewArraySchema()
+	array.Items = bazNestedRef
+	bazNested := &openapi3.Schema{Properties: map[string]*openapi3.SchemaRef{
+		"bazArray": {
+			Value: &openapi3.Schema{
+				Items: bazNestedRef,
+			},
+		},
+		"baz": bazNestedRef,
+	}}
+	bazNestedRef.Value = bazNested
+
 	want := &openapi3.T{
 		OpenAPI: "3.0.3",
 		Info: &openapi3.Info{
@@ -57,6 +70,7 @@ func TestLoadCircularRefFromFile(t *testing.T) {
 			Schemas: openapi3.Schemas{
 				"Foo": foo,
 				"Bar": bar,
+				"Baz": bazNestedRef,
 			},
 		},
 	}
diff --git a/openapi3/loader.go b/openapi3/loader.go
index 452d02ef9..381b38bcd 100644
--- a/openapi3/loader.go
+++ b/openapi3/loader.go
@@ -16,9 +16,6 @@ import (
 	"strings"
 )
 
-var CircularReferenceError = "kin-openapi bug found: circular schema reference not handled"
-var CircularReferenceCounter = 3
-
 func foundUnresolvedRef(ref string) error {
 	return fmt.Errorf("found unresolved ref: %q", ref)
 }
@@ -44,15 +41,9 @@ type Loader struct {
 
 	visitedDocuments map[string]*T
 
-	visitedCallback       map[*Callback]struct{}
-	visitedExample        map[*Example]struct{}
-	visitedHeader         map[*Header]struct{}
-	visitedLink           map[*Link]struct{}
-	visitedParameter      map[*Parameter]struct{}
-	visitedRequestBody    map[*RequestBody]struct{}
-	visitedResponse       map[*Response]struct{}
-	visitedSchema         map[*Schema]struct{}
-	visitedSecurityScheme map[*SecurityScheme]struct{}
+	visitedRefs map[string]struct{}
+	visitedPath []string
+	backtrack   map[string][]func(value any)
 }
 
 // NewLoader returns an empty Loader
@@ -299,6 +290,34 @@ func isSingleRefElement(ref string) bool {
 	return !strings.Contains(ref, "#")
 }
 
+func (loader *Loader) visitRef(ref string) {
+	if loader.visitedRefs == nil {
+		loader.visitedRefs = make(map[string]struct{})
+		loader.backtrack = make(map[string][]func(value any))
+	}
+	loader.visitedPath = append(loader.visitedPath, ref)
+	loader.visitedRefs[ref] = struct{}{}
+}
+
+func (loader *Loader) unvisitRef(ref string, value any) {
+	if value != nil {
+		for _, fn := range loader.backtrack[ref] {
+			fn(value)
+		}
+	}
+	delete(loader.visitedRefs, ref)
+	delete(loader.backtrack, ref)
+	loader.visitedPath = loader.visitedPath[:len(loader.visitedPath)-1]
+}
+
+func (loader *Loader) shouldVisitRef(ref string, fn func(value any)) bool {
+	if _, ok := loader.visitedRefs[ref]; ok {
+		loader.backtrack[ref] = append(loader.backtrack[ref], fn)
+		return false
+	}
+	return true
+}
+
 func (loader *Loader) resolveComponent(doc *T, ref string, path *url.URL, resolved any) (
 	componentDoc *T,
 	componentPath *url.URL,
@@ -535,17 +554,10 @@ func (loader *Loader) resolveHeaderRef(doc *T, component *HeaderRef, documentPat
 		return errMUSTHeader
 	}
 
-	if component.Value != nil {
-		if loader.visitedHeader == nil {
-			loader.visitedHeader = make(map[*Header]struct{})
-		}
-		if _, ok := loader.visitedHeader[component.Value]; ok {
+	if ref := component.Ref; ref != "" {
+		if component.Value != nil {
 			return nil
 		}
-		loader.visitedHeader[component.Value] = struct{}{}
-	}
-
-	if ref := component.Ref; ref != "" {
 		if isSingleRefElement(ref) {
 			var header Header
 			if documentPath, err = loader.loadSingleElementFromURI(ref, documentPath, &header); err != nil {
@@ -554,8 +566,15 @@ func (loader *Loader) resolveHeaderRef(doc *T, component *HeaderRef, documentPat
 			component.Value = &header
 			component.refPath = *documentPath
 		} else {
+			if !loader.shouldVisitRef(ref, func(value any) {
+				component.Value = value.(*Header)
+			}) {
+				return nil
+			}
 			var resolved HeaderRef
+			loader.visitRef(ref)
 			doc, componentPath, err := loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, resolved.Value)
 			if err != nil {
 				return err
 			}
@@ -587,17 +606,10 @@ func (loader *Loader) resolveParameterRef(doc *T, component *ParameterRef, docum
 		return errMUSTParameter
 	}
 
-	if component.Value != nil {
-		if loader.visitedParameter == nil {
-			loader.visitedParameter = make(map[*Parameter]struct{})
-		}
-		if _, ok := loader.visitedParameter[component.Value]; ok {
+	if ref := component.Ref; ref != "" {
+		if component.Value != nil {
 			return nil
 		}
-		loader.visitedParameter[component.Value] = struct{}{}
-	}
-
-	if ref := component.Ref; ref != "" {
 		if isSingleRefElement(ref) {
 			var param Parameter
 			if documentPath, err = loader.loadSingleElementFromURI(ref, documentPath, &param); err != nil {
@@ -606,8 +618,15 @@ func (loader *Loader) resolveParameterRef(doc *T, component *ParameterRef, docum
 			component.Value = &param
 			component.refPath = *documentPath
 		} else {
+			if !loader.shouldVisitRef(ref, func(value any) {
+				component.Value = value.(*Parameter)
+			}) {
+				return nil
+			}
 			var resolved ParameterRef
+			loader.visitRef(ref)
 			doc, componentPath, err := loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, resolved.Value)
 			if err != nil {
 				return err
 			}
@@ -649,17 +668,10 @@ func (loader *Loader) resolveRequestBodyRef(doc *T, component *RequestBodyRef, d
 		return errMUSTRequestBody
 	}
 
-	if component.Value != nil {
-		if loader.visitedRequestBody == nil {
-			loader.visitedRequestBody = make(map[*RequestBody]struct{})
-		}
-		if _, ok := loader.visitedRequestBody[component.Value]; ok {
+	if ref := component.Ref; ref != "" {
+		if component.Value != nil {
 			return nil
 		}
-		loader.visitedRequestBody[component.Value] = struct{}{}
-	}
-
-	if ref := component.Ref; ref != "" {
 		if isSingleRefElement(ref) {
 			var requestBody RequestBody
 			if documentPath, err = loader.loadSingleElementFromURI(ref, documentPath, &requestBody); err != nil {
@@ -668,8 +680,15 @@ func (loader *Loader) resolveRequestBodyRef(doc *T, component *RequestBodyRef, d
 			component.Value = &requestBody
 			component.refPath = *documentPath
 		} else {
+			if !loader.shouldVisitRef(ref, func(value any) {
+				component.Value = value.(*RequestBody)
+			}) {
+				return nil
+			}
 			var resolved RequestBodyRef
+			loader.visitRef(ref)
 			doc, componentPath, err := loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, resolved.Value)
 			if err != nil {
 				return err
 			}
@@ -718,17 +737,10 @@ func (loader *Loader) resolveResponseRef(doc *T, component *ResponseRef, documen
 		return errMUSTResponse
 	}
 
-	if component.Value != nil {
-		if loader.visitedResponse == nil {
-			loader.visitedResponse = make(map[*Response]struct{})
-		}
-		if _, ok := loader.visitedResponse[component.Value]; ok {
+	if ref := component.Ref; ref != "" {
+		if component.Value != nil {
 			return nil
 		}
-		loader.visitedResponse[component.Value] = struct{}{}
-	}
-
-	if ref := component.Ref; ref != "" {
 		if isSingleRefElement(ref) {
 			var resp Response
 			if documentPath, err = loader.loadSingleElementFromURI(ref, documentPath, &resp); err != nil {
@@ -737,8 +749,15 @@ func (loader *Loader) resolveResponseRef(doc *T, component *ResponseRef, documen
 			component.Value = &resp
 			component.refPath = *documentPath
 		} else {
+			if !loader.shouldVisitRef(ref, func(value any) {
+				component.Value = value.(*Response)
+			}) {
+				return nil
+			}
 			var resolved ResponseRef
+			loader.visitRef(ref)
 			doc, componentPath, err := loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, resolved.Value)
 			if err != nil {
 				return err
 			}
@@ -798,17 +817,10 @@ func (loader *Loader) resolveSchemaRef(doc *T, component *SchemaRef, documentPat
 		return errMUSTSchema
 	}
 
-	if component.Value != nil {
-		if loader.visitedSchema == nil {
-			loader.visitedSchema = make(map[*Schema]struct{})
-		}
-		if _, ok := loader.visitedSchema[component.Value]; ok {
+	if ref := component.Ref; ref != "" {
+		if component.Value != nil {
 			return nil
 		}
-		loader.visitedSchema[component.Value] = struct{}{}
-	}
-
-	if ref := component.Ref; ref != "" {
 		if isSingleRefElement(ref) {
 			var schema Schema
 			if documentPath, err = loader.loadSingleElementFromURI(ref, documentPath, &schema); err != nil {
@@ -817,14 +829,15 @@ func (loader *Loader) resolveSchemaRef(doc *T, component *SchemaRef, documentPat
 			component.Value = &schema
 			component.refPath = *documentPath
 		} else {
-			if visitedLimit(visited, ref) {
-				visited = append(visited, ref)
-				return fmt.Errorf("%s with length %d - %s", CircularReferenceError, len(visited), strings.Join(visited, " -> "))
+			if !loader.shouldVisitRef(ref, func(value any) {
+				component.Value = value.(*Schema)
+			}) {
+				return nil
 			}
-			visited = append(visited, ref)
-
 			var resolved SchemaRef
+			loader.visitRef(ref)
 			doc, componentPath, err := loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, resolved.Value)
 			if err != nil {
 				return err
 			}
@@ -837,10 +850,6 @@ func (loader *Loader) resolveSchemaRef(doc *T, component *SchemaRef, documentPat
 			component.Value = resolved.Value
 			component.refPath = resolved.refPath
 		}
-		if loader.visitedSchema == nil {
-			loader.visitedSchema = make(map[*Schema]struct{})
-		}
-		loader.visitedSchema[component.Value] = struct{}{}
 	}
 	value := component.Value
 	if value == nil {
@@ -891,17 +900,10 @@ func (loader *Loader) resolveSecuritySchemeRef(doc *T, component *SecurityScheme
 		return errMUSTSecurityScheme
 	}
 
-	if component.Value != nil {
-		if loader.visitedSecurityScheme == nil {
-			loader.visitedSecurityScheme = make(map[*SecurityScheme]struct{})
-		}
-		if _, ok := loader.visitedSecurityScheme[component.Value]; ok {
+	if ref := component.Ref; ref != "" {
+		if component.Value != nil {
 			return nil
 		}
-		loader.visitedSecurityScheme[component.Value] = struct{}{}
-	}
-
-	if ref := component.Ref; ref != "" {
 		if isSingleRefElement(ref) {
 			var scheme SecurityScheme
 			if _, err = loader.loadSingleElementFromURI(ref, documentPath, &scheme); err != nil {
@@ -910,8 +912,15 @@ func (loader *Loader) resolveSecuritySchemeRef(doc *T, component *SecurityScheme
 			component.Value = &scheme
 			component.refPath = *documentPath
 		} else {
+			if !loader.shouldVisitRef(ref, func(value any) {
+				component.Value = value.(*SecurityScheme)
+			}) {
+				return nil
+			}
 			var resolved SecuritySchemeRef
+			loader.visitRef(ref)
 			doc, componentPath, err := loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, resolved.Value)
 			if err != nil {
 				return err
 			}
@@ -929,21 +938,10 @@ func (loader *Loader) resolveSecuritySchemeRef(doc *T, component *SecurityScheme
 }
 
 func (loader *Loader) resolveExampleRef(doc *T, component *ExampleRef, documentPath *url.URL) (err error) {
-	if component.isEmpty() {
-		return errMUSTExample
-	}
-
-	if component.Value != nil {
-		if loader.visitedExample == nil {
-			loader.visitedExample = make(map[*Example]struct{})
-		}
-		if _, ok := loader.visitedExample[component.Value]; ok {
+	if ref := component.Ref; ref != "" {
+		if component.Value != nil {
 			return nil
 		}
-		loader.visitedExample[component.Value] = struct{}{}
-	}
-
-	if ref := component.Ref; ref != "" {
 		if isSingleRefElement(ref) {
 			var example Example
 			if _, err = loader.loadSingleElementFromURI(ref, documentPath, &example); err != nil {
@@ -952,8 +950,15 @@ func (loader *Loader) resolveExampleRef(doc *T, component *ExampleRef, documentP
 			component.Value = &example
 			component.refPath = *documentPath
 		} else {
+			if !loader.shouldVisitRef(ref, func(value any) {
+				component.Value = value.(*Example)
+			}) {
+				return nil
+			}
 			var resolved ExampleRef
+			loader.visitRef(ref)
 			doc, componentPath, err := loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, resolved.Value)
 			if err != nil {
 				return err
 			}
@@ -975,17 +980,10 @@ func (loader *Loader) resolveCallbackRef(doc *T, component *CallbackRef, documen
 		return errMUSTCallback
 	}
 
-	if component.Value != nil {
-		if loader.visitedCallback == nil {
-			loader.visitedCallback = make(map[*Callback]struct{})
-		}
-		if _, ok := loader.visitedCallback[component.Value]; ok {
+	if ref := component.Ref; ref != "" {
+		if component.Value != nil {
 			return nil
 		}
-		loader.visitedCallback[component.Value] = struct{}{}
-	}
-
-	if ref := component.Ref; ref != "" {
 		if isSingleRefElement(ref) {
 			var resolved Callback
 			if documentPath, err = loader.loadSingleElementFromURI(ref, documentPath, &resolved); err != nil {
@@ -994,8 +992,15 @@ func (loader *Loader) resolveCallbackRef(doc *T, component *CallbackRef, documen
 			component.Value = &resolved
 			component.refPath = *documentPath
 		} else {
+			if !loader.shouldVisitRef(ref, func(value any) {
+				component.Value = value.(*Callback)
+			}) {
+				return nil
+			}
 			var resolved CallbackRef
+			loader.visitRef(ref)
 			doc, componentPath, err := loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, resolved.Value)
 			if err != nil {
 				return err
 			}
@@ -1027,17 +1032,10 @@ func (loader *Loader) resolveLinkRef(doc *T, component *LinkRef, documentPath *u
 		return errMUSTLink
 	}
 
-	if component.Value != nil {
-		if loader.visitedLink == nil {
-			loader.visitedLink = make(map[*Link]struct{})
-		}
-		if _, ok := loader.visitedLink[component.Value]; ok {
+	if ref := component.Ref; ref != "" {
+		if component.Value != nil {
 			return nil
 		}
-		loader.visitedLink[component.Value] = struct{}{}
-	}
-
-	if ref := component.Ref; ref != "" {
 		if isSingleRefElement(ref) {
 			var link Link
 			if _, err = loader.loadSingleElementFromURI(ref, documentPath, &link); err != nil {
@@ -1046,8 +1044,15 @@ func (loader *Loader) resolveLinkRef(doc *T, component *LinkRef, documentPath *u
 			component.Value = &link
 			component.refPath = *documentPath
 		} else {
+			if !loader.shouldVisitRef(ref, func(value any) {
+				component.Value = value.(*Link)
+			}) {
+				return nil
+			}
 			var resolved LinkRef
+			loader.visitRef(ref)
 			doc, componentPath, err := loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, resolved.Value)
 			if err != nil {
 				return err
 			}
@@ -1081,8 +1086,16 @@ func (loader *Loader) resolvePathItemRef(doc *T, pathItem *PathItem, documentPat
 			}
 			*pathItem = p
 		} else {
+			if !loader.shouldVisitRef(ref, func(value any) {
+				*pathItem = *value.(*PathItem)
+			}) {
+				return nil
+			}
 			var resolved PathItem
-			if doc, documentPath, err = loader.resolveComponent(doc, ref, documentPath, &resolved); err != nil {
+			loader.visitRef(ref)
+			doc, documentPath, err = loader.resolveComponent(doc, ref, documentPath, &resolved)
+			defer loader.unvisitRef(ref, &resolved)
+			if err != nil {
 				if err == errMUSTPathItem {
 					return nil
 				}
@@ -1126,16 +1139,3 @@ func (loader *Loader) resolvePathItemRef(doc *T, pathItem *PathItem, documentPat
 func unescapeRefString(ref string) string {
 	return strings.Replace(strings.Replace(ref, "~1", "/", -1), "~0", "~", -1)
 }
-
-func visitedLimit(visited []string, ref string) bool {
-	visitedCount := 0
-	for _, v := range visited {
-		if v == ref {
-			visitedCount++
-			if visitedCount >= CircularReferenceCounter {
-				return true
-			}
-		}
-	}
-	return false
-}
diff --git a/openapi3/schema_formats.go b/openapi3/schema_formats.go
index ea38400c2..655c6296c 100644
--- a/openapi3/schema_formats.go
+++ b/openapi3/schema_formats.go
@@ -2,9 +2,8 @@ package openapi3
 
 import (
 	"fmt"
-	"net"
+	"net/netip"
 	"regexp"
-	"strings"
 )
 
 const (
@@ -43,23 +42,16 @@ func DefineStringFormatCallback(name string, callback FormatCallback) {
 	SchemaStringFormats[name] = Format{callback: callback}
 }
 
-func validateIP(ip string) error {
-	parsed := net.ParseIP(ip)
-	if parsed == nil {
+func validateIPv4(ip string) error {
+	addr, err := netip.ParseAddr(ip)
+	if err != nil {
 		return &SchemaError{
 			Value:  ip,
-			Reason: "Not an IP address",
+			Reason: "Not an IPv4 address",
+			Origin: err,
 		}
 	}
-	return nil
-}
-
-func validateIPv4(ip string) error {
-	if err := validateIP(ip); err != nil {
-		return err
-	}
-
-	if !(strings.Count(ip, ":") < 2) {
+	if !addr.Is4() {
 		return &SchemaError{
 			Value:  ip,
 			Reason: "Not an IPv4 address (it's IPv6)",
@@ -69,11 +61,15 @@ func validateIPv4(ip string) error {
 }
 
 func validateIPv6(ip string) error {
-	if err := validateIP(ip); err != nil {
-		return err
+	addr, err := netip.ParseAddr(ip)
+	if err != nil {
+		return &SchemaError{
+			Value:  ip,
+			Reason: "Not an IPv4 address",
+			Origin: err,
+		}
 	}
-
-	if !(strings.Count(ip, ":") >= 2) {
+	if !addr.Is6() {
 		return &SchemaError{
 			Value:  ip,
 			Reason: "Not an IPv6 address (it's IPv4)",
diff --git a/openapi3/schema_formats_test.go b/openapi3/schema_formats_test.go
index bec98e427..ac9ba644f 100644
--- a/openapi3/schema_formats_test.go
+++ b/openapi3/schema_formats_test.go
@@ -39,6 +39,7 @@ func TestIssue430(t *testing.T) {
 		"::FFFF:192.168.0.1": false,
 		// "[::FFFF:C0A8:1]:80" doesn't parse per net.ParseIP()
 		// "[::FFFF:C0A8:1%1]:80" doesn't parse per net.ParseIP()
+		"2001:db8::": false,
 	}
 
 	for datum := range data {
@@ -53,11 +54,11 @@ func TestIssue430(t *testing.T) {
 		err = schema.VisitJSON(datum)
 		require.NoError(t, err)
 		if isV4 {
-			require.Nil(t, validateIPv4(datum), "%q should be IPv4", datum)
-			require.NotNil(t, validateIPv6(datum), "%q should not be IPv6", datum)
+			assert.Nil(t, validateIPv4(datum), "%q should be IPv4", datum)
+			assert.NotNil(t, validateIPv6(datum), "%q should not be IPv6", datum)
 		} else {
-			require.NotNil(t, validateIPv4(datum), "%q should not be IPv4", datum)
-			require.Nil(t, validateIPv6(datum), "%q should be IPv6", datum)
+			assert.NotNil(t, validateIPv4(datum), "%q should not be IPv4", datum)
+			assert.Nil(t, validateIPv6(datum), "%q should be IPv6", datum)
 		}
 	}
 }
diff --git a/openapi3/testdata/circularRef/base.yml b/openapi3/testdata/circularRef/base.yml
index ff8240eb0..897a45f37 100644
--- a/openapi3/testdata/circularRef/base.yml
+++ b/openapi3/testdata/circularRef/base.yml
@@ -14,3 +14,5 @@ components:
       properties:
         foo:
           $ref: "#/components/schemas/Foo"
+    Baz:
+      $ref: "./baz.yml#/BazNested"
diff --git a/openapi3/testdata/circularRef/baz.yml b/openapi3/testdata/circularRef/baz.yml
new file mode 100644
index 000000000..fb8c85420
--- /dev/null
+++ b/openapi3/testdata/circularRef/baz.yml
@@ -0,0 +1,9 @@
+BazNested:
+  type: object
+  properties:
+    baz:
+      $ref: "#/BazNested"
+    bazArray:
+      type: array
+      items:
+        $ref: "#/BazNested"