diff --git a/backend/app/models/repository_scan.py b/backend/app/models/repository_scan.py
index 976ddda..ce23679 100644
--- a/backend/app/models/repository_scan.py
+++ b/backend/app/models/repository_scan.py
@@ -8,7 +8,7 @@
 class RepoLibrary(BaseModel):
     library_name: str = Field(..., description='Discovered library name')
     library_version: str = Field(..., description='Discovered library version')
-    ecosystem: str = Field(..., description='Ecosystem of the library (e.g., npm, pip, maven, etc.)')
+    ecosystem: Optional[str] = Field(None, description='Ecosystem of the library (e.g., npm, pip, maven, etc.). May be null for legacy records')
     model_config = ConfigDict(populate_by_name=True)
 
 
diff --git a/backend/app/views/library_view.py b/backend/app/views/library_view.py
index ef9c42f..7b36a80 100644
--- a/backend/app/views/library_view.py
+++ b/backend/app/views/library_view.py
@@ -419,7 +419,7 @@ async def handle_repo_scan_highest_risk(payload: dict):
             lib_entry = {
                 "library_name": d.get('name'),
                 "library_version": normalize_version(d.get('version')) or d.get('version') or "unknown",
-                "ecosystem": d.get('ecosystem')
+                "ecosystem": d.get('ecosystem') or 'unknown'
             }
             grouped.setdefault(path, []).append(lib_entry)