diff --git a/client/llb/sourcemap.go b/client/llb/sourcemap.go
index 721db3cebe9d..4e3be2b49936 100644
--- a/client/llb/sourcemap.go
+++ b/client/llb/sourcemap.go
@@ -1,6 +1,7 @@
 package llb
 
 import (
+	"bytes"
 	"context"
 
 	"github.com/moby/buildkit/solver/pb"
@@ -47,6 +48,33 @@ func (s *SourceMap) Location(r []*pb.Range) ConstraintsOpt {
 	})
 }
 
+func equalSourceMap(sm1, sm2 *SourceMap) (out bool) {
+	if sm1 == nil || sm2 == nil {
+		return false
+	}
+	if sm1.Filename != sm2.Filename {
+		return false
+	}
+	if sm1.Language != sm2.Language {
+		return false
+	}
+	if len(sm1.Data) != len(sm2.Data) {
+		return false
+	}
+	if !bytes.Equal(sm1.Data, sm2.Data) {
+		return false
+	}
+	if sm1.Definition != nil && sm2.Definition != nil {
+		if len(sm1.Definition.Def) != len(sm2.Definition.Def) && len(sm1.Definition.Def) != 0 {
+			return false
+		}
+		if !bytes.Equal(sm1.Definition.Def[len(sm1.Definition.Def)-1], sm2.Definition.Def[len(sm2.Definition.Def)-1]) {
+			return false
+		}
+	}
+	return true
+}
+
 type SourceLocation struct {
 	SourceMap *SourceMap
 	Ranges    []*pb.Range
@@ -69,8 +97,18 @@ func (smc *sourceMapCollector) Add(dgst digest.Digest, ls []*SourceLocation) {
 	for _, l := range ls {
 		idx, ok := smc.index[l.SourceMap]
 		if !ok {
-			idx = len(smc.maps)
-			smc.maps = append(smc.maps, l.SourceMap)
+			idx = -1
+			// slow equality check
+			for i, m := range smc.maps {
+				if equalSourceMap(m, l.SourceMap) {
+					idx = i
+					break
+				}
+			}
+			if idx == -1 {
+				idx = len(smc.maps)
+				smc.maps = append(smc.maps, l.SourceMap)
+			}
 		}
 		smc.index[l.SourceMap] = idx
 	}
diff --git a/frontend/dockerfile/dockerfile_provenance_test.go b/frontend/dockerfile/dockerfile_provenance_test.go
index 333b4a2a76f2..fd4de154827b 100644
--- a/frontend/dockerfile/dockerfile_provenance_test.go
+++ b/frontend/dockerfile/dockerfile_provenance_test.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -16,16 +17,20 @@ import (
 
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/content/local"
+	"github.com/containerd/containerd/content/proxy"
 	"github.com/containerd/containerd/platforms"
 	"github.com/containerd/continuity/fs/fstest"
 	intoto "github.com/in-toto/in-toto-golang/in_toto"
 	provenanceCommon "github.com/in-toto/in-toto-golang/in_toto/slsa_provenance/common"
+	controlapi "github.com/moby/buildkit/api/services/control"
 	"github.com/moby/buildkit/client"
 	"github.com/moby/buildkit/client/llb"
 	"github.com/moby/buildkit/exporter/containerimage/exptypes"
 	"github.com/moby/buildkit/frontend/dockerui"
 	gateway "github.com/moby/buildkit/frontend/gateway/client"
+	"github.com/moby/buildkit/identity"
 	"github.com/moby/buildkit/solver/llbsolver/provenance"
+	"github.com/moby/buildkit/solver/pb"
 	"github.com/moby/buildkit/util/contentutil"
 	"github.com/moby/buildkit/util/testutil"
 	"github.com/moby/buildkit/util/testutil/integration"
@@ -1113,3 +1118,153 @@ func testDockerIgnoreMissingProvenance(t *testing.T, sb integration.Sandbox) {
 	}, "", frontend, nil)
 	require.NoError(t, err)
 }
+
+func testFrontendDeduplicateSources(t *testing.T, sb integration.Sandbox) {
+	ctx := sb.Context()
+
+	c, err := client.New(ctx, sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	dockerfile := []byte(`
+FROM scratch as base
+COPY foo foo2
+
+FROM linked
+COPY bar bar2
+`)
+
+	dir := integration.Tmpdir(
+		t,
+		fstest.CreateFile("Dockerfile", dockerfile, 0600),
+		fstest.CreateFile("foo", []byte("data"), 0600),
+		fstest.CreateFile("bar", []byte("data2"), 0600),
+	)
+
+	f := getFrontend(t, sb)
+
+	b := func(ctx context.Context, c gateway.Client) (*gateway.Result, error) {
+		res, err := f.SolveGateway(ctx, c, gateway.SolveRequest{
+			FrontendOpt: map[string]string{
+				"target": "base",
+			},
+		})
+		if err != nil {
+			return nil, err
+		}
+		ref, err := res.SingleRef()
+		if err != nil {
+			return nil, err
+		}
+		st, err := ref.ToState()
+		if err != nil {
+			return nil, err
+		}
+
+		def, err := st.Marshal(ctx)
+		if err != nil {
+			return nil, err
+		}
+
+		dt, ok := res.Metadata["containerimage.config"]
+		if !ok {
+			return nil, errors.Errorf("no containerimage.config in metadata")
+		}
+
+		dt, err = json.Marshal(map[string][]byte{
+			"containerimage.config": dt,
+		})
+		if err != nil {
+			return nil, err
+		}
+
+		res, err = f.SolveGateway(ctx, c, gateway.SolveRequest{
+			FrontendOpt: map[string]string{
+				"context:linked":        "input:baseinput",
+				"input-metadata:linked": string(dt),
+			},
+			FrontendInputs: map[string]*pb.Definition{
+				"baseinput": def.ToPB(),
+			},
+		})
+		if err != nil {
+			return nil, err
+		}
+		return res, nil
+	}
+
+	product := "buildkit_test"
+
+	destDir := t.TempDir()
+
+	ref := identity.NewID()
+
+	_, err = c.Build(ctx, client.SolveOpt{
+		LocalDirs: map[string]string{
+			dockerui.DefaultLocalNameDockerfile: dir,
+			dockerui.DefaultLocalNameContext:    dir,
+		},
+		Exports: []client.ExportEntry{
+			{
+				Type:      client.ExporterLocal,
+				OutputDir: destDir,
+			},
+		},
+		Ref: ref,
+	}, product, b, nil)
+	require.NoError(t, err)
+
+	dt, err := os.ReadFile(filepath.Join(destDir, "foo2"))
+	require.NoError(t, err)
+	require.Equal(t, "data", string(dt))
+
+	dt, err = os.ReadFile(filepath.Join(destDir, "bar2"))
+	require.NoError(t, err)
+	require.Equal(t, "data2", string(dt))
+
+	history, err := c.ControlClient().ListenBuildHistory(ctx, &controlapi.BuildHistoryRequest{
+		Ref:       ref,
+		EarlyExit: true,
+	})
+	require.NoError(t, err)
+
+	store := proxy.NewContentStore(c.ContentClient())
+
+	var provDt []byte
+	for {
+		ev, err := history.Recv()
+		if err != nil {
+			require.Equal(t, io.EOF, err)
+			break
+		}
+		require.Equal(t, ref, ev.Record.Ref)
+
+		for _, prov := range ev.Record.Result.Attestations {
+			if len(prov.Annotations) == 0 || prov.Annotations["in-toto.io/predicate-type"] != "https://slsa.dev/provenance/v0.2" {
+				t.Logf("skipping non-slsa provenance: %s", prov.MediaType)
+				continue
+			}
+
+			provDt, err = content.ReadBlob(ctx, store, ocispecs.Descriptor{
+				MediaType: prov.MediaType,
+				Digest:    prov.Digest,
+				Size:      prov.Size_,
+			})
+			require.NoError(t, err)
+		}
+	}
+
+	require.NotEqual(t, len(provDt), 0)
+
+	var pred provenance.ProvenancePredicate
+	require.NoError(t, json.Unmarshal(provDt, &pred))
+
+	sources := pred.Metadata.BuildKitMetadata.Source.Infos
+
+	require.Equal(t, 1, len(sources))
+	require.Equal(t, "Dockerfile", sources[0].Filename)
+	require.Equal(t, "Dockerfile", sources[0].Language)
+
+	require.Equal(t, dockerfile, sources[0].Data)
+	require.NotEqual(t, 0, len(sources[0].Definition))
+}
diff --git a/frontend/dockerfile/dockerfile_test.go b/frontend/dockerfile/dockerfile_test.go
index 6ae527d01d7a..8abe4f321004 100644
--- a/frontend/dockerfile/dockerfile_test.go
+++ b/frontend/dockerfile/dockerfile_test.go
@@ -170,6 +170,7 @@ var allTests = integration.TestFuncs(
 	testMultiPlatformWarnings,
 	testNilContextInSolveGateway,
 	testCopyUnicodePath,
+	testFrontendDeduplicateSources,
 )
 
 // Tests that depend on the `security.*` entitlements