diff --git a/cmd/worker/workercmd/cmd.go b/cmd/worker/workercmd/cmd.go
index 2aa2522d..483e0816 100644
--- a/cmd/worker/workercmd/cmd.go
+++ b/cmd/worker/workercmd/cmd.go
@@ -70,6 +70,10 @@ func (m *Main) Run(ctx context.Context) error {
 		activities.NewMetadataValidationActivity().Execute,
 		temporalsdk_activity.RegisterOptions{Name: activities.MetadataValidationName},
 	)
+	w.RegisterActivityWithOptions(
+		activities.NewCombinePremisActivity().Execute,
+		temporalsdk_activity.RegisterOptions{Name: activities.CombinePremisName},
+	)
 	w.RegisterActivityWithOptions(
 		activities.NewSipCreationActivity().Execute,
 		temporalsdk_activity.RegisterOptions{Name: activities.SipCreationName},
diff --git a/internal/activities/combine_premis.go b/internal/activities/combine_premis.go
new file mode 100644
index 00000000..6039afb2
--- /dev/null
+++ b/internal/activities/combine_premis.go
@@ -0,0 +1,30 @@
+package activities
+
+import (
+	"context"
+)
+
+const CombinePremisName = "combine-premis"
+
+type CombinePremisActivity struct{}
+
+func NewCombinePremisActivity() *CombinePremisActivity {
+	return &CombinePremisActivity{}
+}
+
+type CombinePremisParams struct {
+	SipPath string
+}
+
+type CombinePremisResult struct {
+	Out string
+}
+
+func (md *CombinePremisActivity) Execute(
+	ctx context.Context,
+	params *CombinePremisParams,
+) (*CombinePremisResult, error) {
+	res := &CombinePremisResult{}
+	res.Out = "OK"
+	return res, nil
+}
diff --git a/internal/workflow/preprocessing.go b/internal/workflow/preprocessing.go
index 40be3d33..106d2edf 100644
--- a/internal/workflow/preprocessing.go
+++ b/internal/workflow/preprocessing.go
@@ -102,6 +102,16 @@ func (w *PreprocessingWorkflow) Execute(
 		return nil, e
 	}
 
+	// Combine PREMIS files into one.
+	var combinePremis activities.CombinePremisResult
+	e = temporalsdk_workflow.ExecuteActivity(withLocalActOpts(ctx), activities.CombinePremisName, &activities.CombinePremisParams{
+		SipPath: localPath,
+	}).
+		Get(ctx, &combinePremis)
+	if e != nil {
+		return nil, e
+	}
+
 	// Repackage SFA SIP into a Bag.
 	var sipCreation activities.SipCreationResult
 	e = temporalsdk_workflow.ExecuteActivity(withLocalActOpts(ctx), activities.SipCreationName, &activities.SipCreationParams{
diff --git a/internal/workflow/preprocessing_test.go b/internal/workflow/preprocessing_test.go
index b5cfa17b..3c68f3c0 100644
--- a/internal/workflow/preprocessing_test.go
+++ b/internal/workflow/preprocessing_test.go
@@ -41,6 +41,10 @@ func (s *PreprocessingTestSuite) SetupTest(cfg config.Configuration) {
 		activities.NewMetadataValidationActivity().Execute,
 		temporalsdk_activity.RegisterOptions{Name: activities.MetadataValidationName},
 	)
+	s.env.RegisterActivityWithOptions(
+		activities.NewCombinePremisActivity().Execute,
+		temporalsdk_activity.RegisterOptions{Name: activities.CombinePremisName},
+	)
 	s.env.RegisterActivityWithOptions(
 		activities.NewSipCreationActivity().Execute,
 		temporalsdk_activity.RegisterOptions{Name: activities.SipCreationName},
@@ -91,6 +95,13 @@ func (s *PreprocessingTestSuite) TestExecute() {
 	).Return(
 		&activities.MetadataValidationResult{}, nil,
 	)
+	s.env.OnActivity(
+		activities.CombinePremisName,
+		sessionCtx,
+		&activities.CombinePremisParams{SipPath: sipPath},
+	).Return(
+		&activities.CombinePremisResult{}, nil,
+	)
 	s.env.OnActivity(
 		activities.SipCreationName,
 		sessionCtx,