diff --git a/builder.go b/builder.go
index f429068d1..c4872d42b 100644
--- a/builder.go
+++ b/builder.go
@@ -108,13 +108,6 @@ func (b *Builder) Build() (*files.BuildMetadata, error) {
 		b.Logger.Debugf("Finished running build for buildpack %s", bp)
 	}
 
-	if b.PlatformAPI.LessThan("0.4") {
-		b.Logger.Debug("Updating BOM entries")
-		for i := range launchBOM {
-			launchBOM[i].ConvertMetadataToVersion()
-		}
-	}
-
 	if b.PlatformAPI.AtLeast("0.8") {
 		b.Logger.Debug("Copying SBOM files")
 		if err := b.copySBOMFiles(inputs.LayersDir, bomFiles); err != nil {
diff --git a/builder_test.go b/builder_test.go
index 6fb823fc2..190e6f692 100644
--- a/builder_test.go
+++ b/builder_test.go
@@ -952,51 +952,6 @@ func testBuilder(t *testing.T, when spec.G, it spec.S) {
 			})
 		})
 
-		when("platform api < 0.4", func() {
-			it.Before(func() {
-				builder.PlatformAPI = api.MustParse("0.3")
-			})
-
-			when("build metadata", func() {
-				when("bom", func() {
-					it("converts metadata.version to top level version", func() {
-						bpA := &buildpack.BpDescriptor{Buildpack: buildpack.BpInfo{BaseInfo: buildpack.BaseInfo{ID: "A", Version: "v1"}}}
-						dirStore.EXPECT().LookupBp("A", "v1").Return(bpA, nil)
-						executor.EXPECT().Build(*bpA, gomock.Any(), gomock.Any()).Return(buildpack.BuildOutputs{
-							LaunchBOM: []buildpack.BOMEntry{
-								{
-									Require: buildpack.Require{
-										Name:     "dep1",
-										Metadata: map[string]interface{}{"version": string("v1")},
-									},
-									Buildpack: buildpack.GroupElement{ID: "A", Version: "v1"},
-								},
-							},
-						}, nil)
-						bpB := &buildpack.BpDescriptor{Buildpack: buildpack.BpInfo{BaseInfo: buildpack.BaseInfo{ID: "B", Version: "v1"}}}
-						dirStore.EXPECT().LookupBp("B", "v2").Return(bpB, nil)
-						executor.EXPECT().Build(*bpB, gomock.Any(), gomock.Any())
-
-						metadata, err := builder.Build()
-						h.AssertNil(t, err)
-
-						if s := cmp.Diff(metadata.BOM, []buildpack.BOMEntry{
-							{
-								Require: buildpack.Require{
-									Name:     "dep1",
-									Version:  "v1",
-									Metadata: map[string]interface{}{"version": string("v1")},
-								},
-								Buildpack: buildpack.GroupElement{ID: "A", Version: "v1"},
-							},
-						}); s != "" {
-							t.Fatalf("Unexpected:\n%s\n", s)
-						}
-					})
-				})
-			})
-		})
-
 		when("platform api < 0.6", func() {
 			it.Before(func() {
 				builder.PlatformAPI = api.MustParse("0.5")
diff --git a/buildpack/bom.go b/buildpack/bom.go
index d1b9f8a8f..e48e12327 100644
--- a/buildpack/bom.go
+++ b/buildpack/bom.go
@@ -1,7 +1,6 @@
 package buildpack
 
 import (
-	"errors"
 	"fmt"
 
 	"github.com/buildpacks/lifecycle/log"
@@ -11,7 +10,8 @@ type BOMValidator interface {
 	ValidateBOM(GroupElement, []BOMEntry) ([]BOMEntry, error)
 }
 
-func NewBOMValidator(bpAPI string, layersDir string, logger log.Logger) BOMValidator {
+// NewBOMValidator returns a validator for the legacy unstructured BOM.
+func NewBOMValidator(_ string, layersDir string, logger log.Logger) BOMValidator {
 	return &defaultBOMValidator{logger: logger, layersDir: layersDir}
 }
 
@@ -55,57 +55,6 @@ func (v *defaultBOMValidator) processBOM(buildpack GroupElement, bom []BOMEntry)
 	return WithBuildpack(buildpack, bom)
 }
 
-type v05To06BOMValidator struct{}
-
-func (v *v05To06BOMValidator) ValidateBOM(bp GroupElement, bom []BOMEntry) ([]BOMEntry, error) {
-	if err := v.validateBOM(bom); err != nil {
-		return []BOMEntry{}, err
-	}
-	return v.processBOM(bp, bom), nil
-}
-
-func (v *v05To06BOMValidator) validateBOM(bom []BOMEntry) error {
-	for _, entry := range bom {
-		if entry.Version != "" {
-			return fmt.Errorf("bom entry '%s' has a top level version which is not allowed. The buildpack should instead set metadata.version", entry.Name)
-		}
-	}
-	return nil
-}
-
-func (v *v05To06BOMValidator) processBOM(buildpack GroupElement, bom []BOMEntry) []BOMEntry {
-	return WithBuildpack(buildpack, bom)
-}
-
-type legacyBOMValidator struct{}
-
-func (v *legacyBOMValidator) ValidateBOM(bp GroupElement, bom []BOMEntry) ([]BOMEntry, error) {
-	if err := v.validateBOM(bom); err != nil {
-		return []BOMEntry{}, err
-	}
-	return v.processBOM(bp, bom), nil
-}
-
-func (v *legacyBOMValidator) validateBOM(bom []BOMEntry) error {
-	for _, entry := range bom {
-		if version, ok := entry.Metadata["version"]; ok {
-			metadataVersion := fmt.Sprintf("%v", version)
-			if entry.Version != "" && entry.Version != metadataVersion {
-				return errors.New("top level version does not match metadata version")
-			}
-		}
-	}
-	return nil
-}
-
-func (v *legacyBOMValidator) processBOM(buildpack GroupElement, bom []BOMEntry) []BOMEntry {
-	bom = WithBuildpack(buildpack, bom)
-	for i := range bom {
-		bom[i].convertVersionToMetadata()
-	}
-	return bom
-}
-
 func WithBuildpack(bp GroupElement, bom []BOMEntry) []BOMEntry {
 	var out []BOMEntry
 	for _, entry := range bom {
diff --git a/buildpack/build.go b/buildpack/build.go
index 993de16e6..f5e3258c5 100644
--- a/buildpack/build.go
+++ b/buildpack/build.go
@@ -64,13 +64,6 @@ type BuildExecutor interface {
 type DefaultBuildExecutor struct{}
 
 func (e *DefaultBuildExecutor) Build(d BpDescriptor, inputs BuildInputs, logger log.Logger) (BuildOutputs, error) {
-	if api.MustParse(d.WithAPI).Equal(api.MustParse("0.2")) {
-		logger.Debug("Updating plan entries")
-		for i := range inputs.Plan.Entries {
-			inputs.Plan.Entries[i].convertMetadataToVersion()
-		}
-	}
-
 	logger.Debug("Creating plan directory")
 	planDir, err := os.MkdirTemp("", launch.EscapeID(d.Buildpack.ID)+"-")
 	if err != nil {
diff --git a/buildpack/detect.go b/buildpack/detect.go
index 34372c6d6..f23c5ef62 100644
--- a/buildpack/detect.go
+++ b/buildpack/detect.go
@@ -57,7 +57,7 @@ func (e *DefaultDetectExecutor) Detect(d Descriptor, inputs DetectInputs, logger
 	}
 }
 
-func detectBp(d BpDescriptor, inputs DetectInputs, logger log.Logger) DetectOutputs {
+func detectBp(d BpDescriptor, inputs DetectInputs, _ log.Logger) DetectOutputs {
 	planDir, planPath, err := processBuildpackPaths()
 	defer os.RemoveAll(planDir)
 	if err != nil {
@@ -78,7 +78,8 @@ func detectBp(d BpDescriptor, inputs DetectInputs, logger log.Logger) DetectOutp
 		result.Code = -1
 	}
 	if result.hasTopLevelVersions() || result.Or.hasTopLevelVersions() {
-		logger.Warnf(`buildpack %s has a "version" key. This key is deprecated in build plan requirements in buildpack API 0.3. "metadata.version" should be used instead`, d.Buildpack.ID)
+		result.Err = fmt.Errorf(`buildpack %s has a "version" key which is not supported. "metadata.version" should be used instead`, d.Buildpack.ID)
+		result.Code = -1
 	}
 
 	return result
@@ -115,7 +116,8 @@ func detectExt(d ExtDescriptor, inputs DetectInputs, logger log.Logger) DetectOu
 		result.Code = -1
 	}
 	if result.hasTopLevelVersions() || result.Or.hasTopLevelVersions() {
-		logger.Warnf(`extension %s has a "version" key. This key is deprecated in build plan requirements in buildpack API 0.3. "metadata.version" should be used instead`, d.Extension.ID)
+		result.Err = fmt.Errorf(`extension %s has a "version" key which is not supported. "metadata.version" should be used instead`, d.Extension.ID)
+		result.Code = -1
 	}
 	if result.hasRequires() || result.Or.hasRequires() {
 		result.Err = fmt.Errorf(`extension %s outputs "requires" which is not allowed`, d.Extension.ID)
diff --git a/buildpack/detect_test.go b/buildpack/detect_test.go
index 8dd0cc27d..4a4db65f0 100644
--- a/buildpack/detect_test.go
+++ b/buildpack/detect_test.go
@@ -5,7 +5,6 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
-	"strings"
 	"testing"
 
 	"github.com/apex/log"
@@ -216,7 +215,7 @@ func testDetect(t *testing.T, when spec.G, it spec.S) {
 					if err == nil {
 						t.Fatalf("Expected error")
 					}
-					h.AssertEq(t, err.Error(), `buildpack A has a "version" key and a "metadata.version" which cannot be specified together. "metadata.version" should be used instead`)
+					h.AssertEq(t, err.Error(), `buildpack A has a "version" key which is not supported. "metadata.version" should be used instead`)
 				})
 
 				it("errors if there is an alternate plan with both a top level version and a metadata version", func() {
@@ -233,27 +232,23 @@ func testDetect(t *testing.T, when spec.G, it spec.S) {
 					if err == nil {
 						t.Fatalf("Expected error")
 					}
-					h.AssertEq(t, err.Error(), `buildpack A has a "version" key and a "metadata.version" which cannot be specified together. "metadata.version" should be used instead`)
+					h.AssertEq(t, err.Error(), `buildpack A has a "version" key which is not supported. "metadata.version" should be used instead`)
 				})
 
-				it("warns if the plan has a top level version", func() {
+				it("errors if the plan has a top level version", func() {
 					toappfile("\n[[requires]]\n name = \"dep2\"\n version = \"some-version\"", "detect-plan-A-v1.toml")
 
 					detectRun := executor.Detect(descriptor, inputs, logger)
 
-					h.AssertEq(t, detectRun.Code, 0)
+					h.AssertEq(t, detectRun.Code, -1)
 					err := detectRun.Err
-					if err != nil {
-						t.Fatalf("Unexpected error:\n%s\n", err)
-					}
-					if s := h.AllLogs(logHandler); !strings.Contains(s,
-						`buildpack A has a "version" key. This key is deprecated in build plan requirements in buildpack API 0.3. "metadata.version" should be used instead`,
-					) {
-						t.Fatalf("Expected log to contain warning:\n%s\n", s)
+					if err == nil {
+						t.Fatalf("Expected error")
 					}
+					h.AssertEq(t, err.Error(), `buildpack A has a "version" key which is not supported. "metadata.version" should be used instead`)
 				})
 
-				it("warns if there is an alternate plan with a top level version", func() {
+				it("errors if there is an alternate plan with a top level version", func() {
 					toappfile("\n[[provides]]\n name = \"dep2-missing\"", "detect-plan-A-v1.toml")
 					toappfile("\n[[or]]", "detect-plan-A-v1.toml")
 					toappfile("\n[[or.provides]]\n name = \"dep1-present\"", "detect-plan-A-v1.toml")
@@ -261,16 +256,12 @@ func testDetect(t *testing.T, when spec.G, it spec.S) {
 
 					detectRun := executor.Detect(descriptor, inputs, logger)
 
-					h.AssertEq(t, detectRun.Code, 0)
+					h.AssertEq(t, detectRun.Code, -1)
 					err := detectRun.Err
-					if err != nil {
-						t.Fatalf("Unexpected error:\n%s\n", err)
-					}
-					if s := h.AllLogs(logHandler); !strings.Contains(s,
-						`buildpack A has a "version" key. This key is deprecated in build plan requirements in buildpack API 0.3. "metadata.version" should be used instead`,
-					) {
-						t.Fatalf("Expected log to contain warning:\n%s\n", s)
+					if err == nil {
+						t.Fatalf("Expected error")
 					}
+					h.AssertEq(t, err.Error(), `buildpack A has a "version" key which is not supported. "metadata.version" should be used instead`)
 				})
 			})
 
diff --git a/buildpack/files.go b/buildpack/files.go
index 9636e4ebc..bd42a40cd 100644
--- a/buildpack/files.go
+++ b/buildpack/files.go
@@ -108,45 +108,12 @@ type BOMEntry struct {
 	Buildpack GroupElement `toml:"buildpack" json:"buildpack"`
 }
 
-func (bom *BOMEntry) ConvertMetadataToVersion() {
-	if version, ok := bom.Metadata["version"]; ok {
-		metadataVersion := fmt.Sprintf("%v", version)
-		bom.Version = metadataVersion
-	}
-}
-
-func (bom *BOMEntry) convertVersionToMetadata() {
-	if bom.Version != "" {
-		if bom.Metadata == nil {
-			bom.Metadata = make(map[string]interface{})
-		}
-		bom.Metadata["version"] = bom.Version
-		bom.Version = ""
-	}
-}
-
 type Require struct {
 	Name     string                 `toml:"name" json:"name"`
 	Version  string                 `toml:"version,omitempty" json:"version,omitempty"`
 	Metadata map[string]interface{} `toml:"metadata" json:"metadata"`
 }
 
-func (r *Require) convertMetadataToVersion() {
-	if version, ok := r.Metadata["version"]; ok {
-		r.Version = fmt.Sprintf("%v", version)
-	}
-}
-
-func (r *Require) ConvertVersionToMetadata() {
-	if r.Version != "" {
-		if r.Metadata == nil {
-			r.Metadata = make(map[string]interface{})
-		}
-		r.Metadata["version"] = r.Version
-		r.Version = ""
-	}
-}
-
 func (r *Require) hasDoublySpecifiedVersions() bool {
 	if _, ok := r.Metadata["version"]; ok {
 		return r.Version != ""
diff --git a/detector.go b/detector.go
index a0c7ad5cb..f140bb6b8 100644
--- a/detector.go
+++ b/detector.go
@@ -145,11 +145,6 @@ func (d *Detector) DetectOrder(order buildpack.Order) (buildpack.Group, files.Pl
 	} else if err == ErrFailedDetection {
 		err = buildpack.NewError(err, buildpack.ErrTypeFailedDetection)
 	}
-	for i := range planEntries {
-		for j := range planEntries[i].Requires {
-			planEntries[i].Requires[j].ConvertVersionToMetadata()
-		}
-	}
 	return buildpack.Group{Group: filter(detected, buildpack.KindBuildpack), GroupExtensions: filter(detected, buildpack.KindExtension)},
 		files.Plan{Entries: planEntries},
 		err
diff --git a/detector_test.go b/detector_test.go
index f5285ef99..9026c91f3 100644
--- a/detector_test.go
+++ b/detector_test.go
@@ -568,82 +568,6 @@ func testDetector(t *testing.T, when spec.G, it spec.S) {
 			}
 		})
 
-		it("converts top level versions to metadata versions", func() {
-			bpA1 := &buildpack.BpDescriptor{
-				Buildpack: buildpack.BpInfo{BaseInfo: buildpack.BaseInfo{ID: "A", Version: "v1"}},
-			}
-			dirStore.EXPECT().LookupBp("A", "v1").Return(bpA1, nil).AnyTimes()
-
-			bpB1 := &buildpack.BpDescriptor{
-				Buildpack: buildpack.BpInfo{BaseInfo: buildpack.BaseInfo{ID: "B", Version: "v1"}},
-			}
-			dirStore.EXPECT().LookupBp("B", "v1").Return(bpB1, nil).AnyTimes()
-
-			executor.EXPECT().Detect(bpA1, gomock.Any(), gomock.Any())
-			executor.EXPECT().Detect(bpB1, gomock.Any(), gomock.Any())
-
-			group := []buildpack.GroupElement{
-				{ID: "A", Version: "v1"},
-				{ID: "B", Version: "v1"},
-			}
-			resolver.EXPECT().Resolve(group, detector.Runs).Return(group, []files.BuildPlanEntry{
-				{
-					Providers: []buildpack.GroupElement{
-						{ID: "A", Version: "v1"},
-					},
-					Requires: []buildpack.Require{
-						{
-							Name:    "dep1",
-							Version: "some-version",
-						},
-					},
-				},
-				{
-					Providers: []buildpack.GroupElement{
-						{ID: "B", Version: "v1"},
-					},
-					Requires: []buildpack.Require{
-						{
-							Name:     "dep2",
-							Version:  "some-already-exists-version",
-							Metadata: map[string]interface{}{"version": "some-already-exists-version"},
-						},
-					},
-				},
-			}, nil)
-
-			detector.Order = buildpack.Order{{Group: group}}
-			found, plan, err := detector.Detect()
-			if err != nil {
-				t.Fatalf("Unexpected error:\n%s\n", err)
-			}
-
-			if s := cmp.Diff(found, buildpack.Group{Group: group}); s != "" {
-				t.Fatalf("Unexpected group:\n%s\n", s)
-			}
-
-			if !hasEntries(plan.Entries, []files.BuildPlanEntry{
-				{
-					Providers: []buildpack.GroupElement{
-						{ID: "A", Version: "v1"},
-					},
-					Requires: []buildpack.Require{
-						{Name: "dep1", Metadata: map[string]interface{}{"version": "some-version"}},
-					},
-				},
-				{
-					Providers: []buildpack.GroupElement{
-						{ID: "B", Version: "v1"},
-					},
-					Requires: []buildpack.Require{
-						{Name: "dep2", Metadata: map[string]interface{}{"version": "some-already-exists-version"}},
-					},
-				},
-			}) {
-				t.Fatalf("Unexpected entries:\n%+v\n", plan.Entries)
-			}
-		})
-
 		it("updates detect runs for each buildpack", func() {
 			bpA1 := &buildpack.BpDescriptor{
 				Buildpack: buildpack.BpInfo{BaseInfo: buildpack.BaseInfo{ID: "A", Version: "v1"}},