diff --git a/app/api/v1/admin/code_quality.py b/app/api/v1/admin/code_quality.py
index bc82d4e8..96dcd049 100644
--- a/app/api/v1/admin/code_quality.py
+++ b/app/api/v1/admin/code_quality.py
@@ -122,7 +122,7 @@ class DashboardStatsResponse(BaseModel):
     by_rule: dict
     by_module: dict
     top_files: list
-    last_scan: str | None
+    last_scan: str | None = None
 
 
 # API Endpoints
diff --git a/app/services/code_quality_service.py b/app/services/code_quality_service.py
index 6ef18e44..a027eac9 100644
--- a/app/services/code_quality_service.py
+++ b/app/services/code_quality_service.py
@@ -371,6 +371,7 @@ class CodeQualityService:
                 "by_rule": {},
                 "by_module": {},
                 "top_files": [],
+                "last_scan": None,
             }
 
         # Get violation counts by status