diff --git a/client/client_test.go b/client/client_test.go
index 34930288..7fa74105 100644
--- a/client/client_test.go
+++ b/client/client_test.go
@@ -2690,9 +2690,14 @@ func testSourceMap(t *testing.T, sb integration.Sandbox) {
 	require.NoError(t, err)
 	defer c.Close()
 
-	sm := llb.NewSourceMap(nil, "foo", []byte("data"))
+	sm1 := llb.NewSourceMap(nil, "foo", []byte("data1"))
+	sm2 := llb.NewSourceMap(nil, "bar", []byte("data2"))
 
-	st := llb.Scratch().Run(llb.Shlex("not-exist"), sm.Location([]*pb.Range{{Start: pb.Position{Line: 7}}}))
+	st := llb.Scratch().Run(
+		llb.Shlex("not-exist"),
+		sm1.Location([]*pb.Range{{Start: pb.Position{Line: 7}}}),
+		sm2.Location([]*pb.Range{{Start: pb.Position{Line: 8}}}),
+	)
 
 	def, err := st.Marshal(context.TODO())
 	require.NoError(t, err)
@@ -2701,15 +2706,27 @@ func testSourceMap(t *testing.T, sb integration.Sandbox) {
 	require.Error(t, err)
 
 	srcs := errdefs.Sources(err)
-	require.Equal(t, 1, len(srcs))
+	require.Equal(t, 2, len(srcs))
 
-	require.Equal(t, "foo", srcs[0].Info.Filename)
-	require.Equal(t, []byte("data"), srcs[0].Info.Data)
+	// Source errors are wrapped in the order provided as llb.ConstraintOpts, so
+	// when they are unwrapped, the first unwrapped error is the last location
+	// provided.
+	require.Equal(t, "bar", srcs[0].Info.Filename)
+	require.Equal(t, []byte("data2"), srcs[0].Info.Data)
 	require.Nil(t, srcs[0].Info.Definition)
 
-	require.Equal(t, 1, len(srcs[0].Locations))
-	require.Equal(t, int32(7), srcs[0].Locations[0].Start.Line)
-	require.Equal(t, int32(0), srcs[0].Locations[0].Start.Character)
+	require.Equal(t, 1, len(srcs[0].Ranges))
+	require.Equal(t, int32(8), srcs[0].Ranges[0].Start.Line)
+	require.Equal(t, int32(0), srcs[0].Ranges[0].Start.Character)
+
+	require.Equal(t, "foo", srcs[1].Info.Filename)
+	require.Equal(t, []byte("data1"), srcs[1].Info.Data)
+	require.Nil(t, srcs[1].Info.Definition)
+
+	require.Equal(t, 1, len(srcs[1].Ranges))
+	require.Equal(t, int32(7), srcs[1].Ranges[0].Start.Line)
+	require.Equal(t, int32(0), srcs[1].Ranges[0].Start.Character)
+
 }
 
 func testSourceMapFromRef(t *testing.T, sb integration.Sandbox) {
@@ -2774,9 +2791,9 @@ func testSourceMapFromRef(t *testing.T, sb integration.Sandbox) {
 	require.Equal(t, []byte("bardata"), srcs[0].Info.Data)
 	require.NotNil(t, srcs[0].Info.Definition)
 
-	require.Equal(t, 1, len(srcs[0].Locations))
-	require.Equal(t, int32(3), srcs[0].Locations[0].Start.Line)
-	require.Equal(t, int32(1), srcs[0].Locations[0].Start.Character)
+	require.Equal(t, 1, len(srcs[0].Ranges))
+	require.Equal(t, int32(3), srcs[0].Ranges[0].Start.Line)
+	require.Equal(t, int32(1), srcs[0].Ranges[0].Start.Character)
 }
 
 func testProxyEnv(t *testing.T, sb integration.Sandbox) {
diff --git a/client/llb/async.go b/client/llb/async.go
index 20781850..48216e98 100644
--- a/client/llb/async.go
+++ b/client/llb/async.go
@@ -85,7 +85,7 @@ type errVertex struct {
 func (v *errVertex) Validate(context.Context) error {
 	return v.err
 }
-func (v *errVertex) Marshal(context.Context, *Constraints) (digest.Digest, []byte, *pb.OpMetadata, *SourceLocation, error) {
+func (v *errVertex) Marshal(context.Context, *Constraints) (digest.Digest, []byte, *pb.OpMetadata, []*SourceLocation, error) {
 	return "", nil, nil, nil, v.err
 }
 func (v *errVertex) Output() Output {
diff --git a/client/llb/definition.go b/client/llb/definition.go
index 279df87f..fe9f7c17 100644
--- a/client/llb/definition.go
+++ b/client/llb/definition.go
@@ -20,7 +20,7 @@ type DefinitionOp struct {
 	ops       map[digest.Digest]*pb.Op
 	defs      map[digest.Digest][]byte
 	metas     map[digest.Digest]pb.OpMetadata
-	sources   map[digest.Digest]*SourceLocation
+	sources   map[digest.Digest][]*SourceLocation
 	platforms map[digest.Digest]*specs.Platform
 	dgst      digest.Digest
 	index     pb.OutputIndex
@@ -50,7 +50,7 @@ func NewDefinitionOp(def *pb.Definition) (*DefinitionOp, error) {
 		platforms[dgst] = platform
 	}
 
-	srcs := map[digest.Digest]*SourceLocation{}
+	srcs := map[digest.Digest][]*SourceLocation{}
 
 	if def.Source != nil {
 		sourceMaps := make([]*SourceMap, len(def.Source.Infos))
@@ -74,10 +74,10 @@ func NewDefinitionOp(def *pb.Definition) (*DefinitionOp, error) {
 					return nil, errors.Errorf("failed to find source map with index %d", loc.SourceIndex)
 				}
 
-				srcs[digest.Digest(dgst)] = &SourceLocation{
+				srcs[digest.Digest(dgst)] = append(srcs[digest.Digest(dgst)], &SourceLocation{
 					SourceMap: sourceMaps[int(loc.SourceIndex)],
 					Ranges:    loc.Ranges,
-				}
+				})
 			}
 		}
 	}
@@ -144,7 +144,7 @@ func (d *DefinitionOp) Validate(context.Context) error {
 	return nil
 }
 
-func (d *DefinitionOp) Marshal(ctx context.Context, c *Constraints) (digest.Digest, []byte, *pb.OpMetadata, *SourceLocation, error) {
+func (d *DefinitionOp) Marshal(ctx context.Context, c *Constraints) (digest.Digest, []byte, *pb.OpMetadata, []*SourceLocation, error) {
 	if d.dgst == "" {
 		return "", nil, nil, nil, errors.Errorf("cannot marshal empty definition op")
 	}
diff --git a/client/llb/exec.go b/client/llb/exec.go
index 5d5d01e1..0f32e5e3 100644
--- a/client/llb/exec.go
+++ b/client/llb/exec.go
@@ -124,7 +124,7 @@ func (e *ExecOp) Validate(ctx context.Context) error {
 	return nil
 }
 
-func (e *ExecOp) Marshal(ctx context.Context, c *Constraints) (digest.Digest, []byte, *pb.OpMetadata, *SourceLocation, error) {
+func (e *ExecOp) Marshal(ctx context.Context, c *Constraints) (digest.Digest, []byte, *pb.OpMetadata, []*SourceLocation, error) {
 	if e.Cached(c) {
 		return e.Load()
 	}
@@ -358,7 +358,7 @@ func (e *ExecOp) Marshal(ctx context.Context, c *Constraints) (digest.Digest, []
 	if err != nil {
 		return "", nil, nil, nil, err
 	}
-	e.Store(dt, md, e.constraints.Source, c)
+	e.Store(dt, md, e.constraints.SourceLocations, c)
 	return e.Load()
 }
 
diff --git a/client/llb/fileop.go b/client/llb/fileop.go
index 865756ce..db5ed00d 100644
--- a/client/llb/fileop.go
+++ b/client/llb/fileop.go
@@ -649,7 +649,7 @@ func (ms *marshalState) add(fa *FileAction, c *Constraints) (*fileActionState, e
 	return st, nil
 }
 
-func (f *FileOp) Marshal(ctx context.Context, c *Constraints) (digest.Digest, []byte, *pb.OpMetadata, *SourceLocation, error) {
+func (f *FileOp) Marshal(ctx context.Context, c *Constraints) (digest.Digest, []byte, *pb.OpMetadata, []*SourceLocation, error) {
 	if f.Cached(c) {
 		return f.Load()
 	}
@@ -704,7 +704,7 @@ func (f *FileOp) Marshal(ctx context.Context, c *Constraints) (digest.Digest, []
 	if err != nil {
 		return "", nil, nil, nil, err
 	}
-	f.Store(dt, md, f.constraints.Source, c)
+	f.Store(dt, md, f.constraints.SourceLocations, c)
 	return f.Load()
 }
 
diff --git a/client/llb/llbbuild/llbbuild.go b/client/llb/llbbuild/llbbuild.go
index 162985e6..4b99e799 100644
--- a/client/llb/llbbuild/llbbuild.go
+++ b/client/llb/llbbuild/llbbuild.go
@@ -48,7 +48,7 @@ func (b *build) Validate(context.Context) error {
 	return nil
 }
 
-func (b *build) Marshal(ctx context.Context, c *llb.Constraints) (digest.Digest, []byte, *pb.OpMetadata, *llb.SourceLocation, error) {
+func (b *build) Marshal(ctx context.Context, c *llb.Constraints) (digest.Digest, []byte, *pb.OpMetadata, []*llb.SourceLocation, error) {
 	if b.Cached(c) {
 		return b.Load()
 	}
@@ -85,7 +85,7 @@ func (b *build) Marshal(ctx context.Context, c *llb.Constraints) (digest.Digest,
 	if err != nil {
 		return "", nil, nil, nil, err
 	}
-	b.Store(dt, md, b.constraints.Source, c)
+	b.Store(dt, md, b.constraints.SourceLocations, c)
 	return b.Load()
 }
 
diff --git a/client/llb/marshal.go b/client/llb/marshal.go
index 941a755f..282b592b 100644
--- a/client/llb/marshal.go
+++ b/client/llb/marshal.go
@@ -98,20 +98,20 @@ type MarshalCache struct {
 	digest      digest.Digest
 	dt          []byte
 	md          *pb.OpMetadata
-	src         *SourceLocation
+	srcs        []*SourceLocation
 	constraints *Constraints
 }
 
 func (mc *MarshalCache) Cached(c *Constraints) bool {
 	return mc.dt != nil && mc.constraints == c
 }
-func (mc *MarshalCache) Load() (digest.Digest, []byte, *pb.OpMetadata, *SourceLocation, error) {
-	return mc.digest, mc.dt, mc.md, mc.src, nil
+func (mc *MarshalCache) Load() (digest.Digest, []byte, *pb.OpMetadata, []*SourceLocation, error) {
+	return mc.digest, mc.dt, mc.md, mc.srcs, nil
 }
-func (mc *MarshalCache) Store(dt []byte, md *pb.OpMetadata, src *SourceLocation, c *Constraints) {
+func (mc *MarshalCache) Store(dt []byte, md *pb.OpMetadata, srcs []*SourceLocation, c *Constraints) {
 	mc.digest = digest.FromBytes(dt)
 	mc.dt = dt
 	mc.md = md
 	mc.constraints = c
-	mc.src = src
+	mc.srcs = srcs
 }
diff --git a/client/llb/source.go b/client/llb/source.go
index 7eea6e7b..fd2f44f2 100644
--- a/client/llb/source.go
+++ b/client/llb/source.go
@@ -44,7 +44,7 @@ func (s *SourceOp) Validate(ctx context.Context) error {
 	return nil
 }
 
-func (s *SourceOp) Marshal(ctx context.Context, constraints *Constraints) (digest.Digest, []byte, *pb.OpMetadata, *SourceLocation, error) {
+func (s *SourceOp) Marshal(ctx context.Context, constraints *Constraints) (digest.Digest, []byte, *pb.OpMetadata, []*SourceLocation, error) {
 	if s.Cached(constraints) {
 		return s.Load()
 	}
@@ -77,7 +77,7 @@ func (s *SourceOp) Marshal(ctx context.Context, constraints *Constraints) (diges
 		return "", nil, nil, nil, err
 	}
 
-	s.Store(dt, md, s.constraints.Source, constraints)
+	s.Store(dt, md, s.constraints.SourceLocations, constraints)
 	return s.Load()
 }
 
diff --git a/client/llb/sourcemap.go b/client/llb/sourcemap.go
index ecff7e7f..ca180fb6 100644
--- a/client/llb/sourcemap.go
+++ b/client/llb/sourcemap.go
@@ -27,10 +27,10 @@ func (s *SourceMap) Location(r []*pb.Range) ConstraintsOpt {
 		if s == nil {
 			return
 		}
-		c.Source = &SourceLocation{
+		c.SourceLocations = append(c.SourceLocations, &SourceLocation{
 			SourceMap: s,
 			Ranges:    r,
-		}
+		})
 	})
 }
 
@@ -51,14 +51,16 @@ func newSourceMapCollector() *sourceMapCollector {
 	}
 }
 
-func (smc *sourceMapCollector) Add(dgst digest.Digest, l *SourceLocation) {
-	idx, ok := smc.index[l.SourceMap]
-	if !ok {
-		idx = len(smc.maps)
-		smc.maps = append(smc.maps, l.SourceMap)
-		smc.ranges = append(smc.ranges, map[digest.Digest][]*pb.Range{})
+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)
+			smc.ranges = append(smc.ranges, map[digest.Digest][]*pb.Range{})
+		}
+		smc.ranges[idx][dgst] = l.Ranges
 	}
-	smc.ranges[idx][dgst] = l.Ranges
 }
 
 func (smc *sourceMapCollector) Marshal(ctx context.Context, co ...ConstraintsOpt) (*pb.Source, error) {
diff --git a/client/llb/state.go b/client/llb/state.go
index d815b2fb..dac9b871 100644
--- a/client/llb/state.go
+++ b/client/llb/state.go
@@ -24,7 +24,7 @@ type Output interface {
 
 type Vertex interface {
 	Validate(context.Context) error
-	Marshal(context.Context, *Constraints) (digest.Digest, []byte, *pb.OpMetadata, *SourceLocation, error)
+	Marshal(context.Context, *Constraints) (digest.Digest, []byte, *pb.OpMetadata, []*SourceLocation, error)
 	Output() Output
 	Inputs() []Output
 }
@@ -182,7 +182,7 @@ func marshal(ctx context.Context, v Vertex, def *Definition, s *sourceMapCollect
 		}
 	}
 
-	dgst, dt, opMeta, sl, err := v.Marshal(ctx, c)
+	dgst, dt, opMeta, sls, err := v.Marshal(ctx, c)
 	if err != nil {
 		return def, err
 	}
@@ -193,9 +193,7 @@ func marshal(ctx context.Context, v Vertex, def *Definition, s *sourceMapCollect
 	if _, ok := cache[dgst]; ok {
 		return def, nil
 	}
-	if sl != nil {
-		s.Add(dgst, sl)
-	}
+	s.Add(dgst, sls)
 	def.Def = append(def.Def, dt)
 	cache[dgst] = struct{}{}
 	return def, nil
@@ -524,7 +522,7 @@ type Constraints struct {
 	Metadata          pb.OpMetadata
 	LocalUniqueID     string
 	Caps              *apicaps.CapSet
-	Source            *SourceLocation
+	SourceLocations   []*SourceLocation
 }
 
 func Platform(p specs.Platform) ConstraintsOpt {
diff --git a/frontend/dockerfile/errors_test.go b/frontend/dockerfile/errors_test.go
index efbb4c6a..e1f3ca41 100644
--- a/frontend/dockerfile/errors_test.go
+++ b/frontend/dockerfile/errors_test.go
@@ -100,7 +100,7 @@ env bar=baz`,
 
 			require.Equal(t, "Dockerfile", srcs[0].Info.Filename)
 			require.Equal(t, tc.dockerfile, string(srcs[0].Info.Data))
-			require.Equal(t, len(tc.errorLine), len(srcs[0].Locations))
+			require.Equal(t, len(tc.errorLine), len(srcs[0].Ranges))
 			require.NotNil(t, srcs[0].Info.Definition)
 
 		next: