diff --git a/events/dbpersist/dbpersist.go b/events/dbpersist/dbpersist.go
index 04e9fb87..5e47218e 100644
--- a/events/dbpersist/dbpersist.go
+++ b/events/dbpersist/dbpersist.go
@@ -306,6 +306,12 @@ func (p *DbPersistence) RecordFromRepoCommit(ctx context.Context, evt *comatprot
 		return nil, err
 	}
 
+	// Normalize empty string to nil for since field
+	var since *string
+	if evt.Since != nil && *evt.Since != "" {
+		since = evt.Since
+	}
+
 	rer := RepoEventRecord{
 		Commit: &models.DbCID{CID: cid.Cid(evt.Commit)},
 		//Prev
@@ -315,7 +321,7 @@ func (p *DbPersistence) RecordFromRepoCommit(ctx context.Context, evt *comatprot
 		Time:   t,
 		Rebase: evt.Rebase,
 		Rev:    evt.Rev,
-		Since:  evt.Since,
+		Since:  since,
 	}
 
 	opsb, err := json.Marshal(evt.Ops)
@@ -339,6 +345,12 @@ func (p *DbPersistence) RecordFromRepoSync(ctx context.Context, evt *comatproto.
 		return nil, err
 	}
 
+	// Normalize empty string to nil for since field
+	var since *string
+	if evt.Since != nil && *evt.Since != "" {
+		since = evt.Since
+	}
+
 	rer := RepoEventRecord{
 		Repo: uid,
 		Type: "repo_sync",
@@ -555,6 +567,12 @@ func (p *DbPersistence) hydrateCommit(ctx context.Context, rer *RepoEventRecord)
 		return nil, err
 	}
 
+	// Normalize empty string to nil for since field
+	var since *string
+	if rer.Since != nil && *rer.Since != "" {
+		since = rer.Since
+	}
+
 	out := &comatproto.SyncSubscribeRepos_Commit{
 		Seq:    int64(rer.Seq),
 		Repo:   did,
@@ -564,7 +582,7 @@ func (p *DbPersistence) hydrateCommit(ctx context.Context, rer *RepoEventRecord)
 		Rebase: rer.Rebase,
 		Ops:    ops,
 		Rev:    rer.Rev,
-		Since:  rer.Since,
+		Since:  since,
 	}
 
 	cs, err := p.readCarSlice(ctx, rer)