diff --git a/webapp/models/source.py b/webapp/models/source.py
index 9907409b..5c7f33c1 100644
--- a/webapp/models/source.py
+++ b/webapp/models/source.py
@@ -79,4 +79,4 @@ def combined_updated_at(self) -> datetime:
             return self.realtime_data_updated_at
         if self.static_data_updated_at:
             return self.static_data_updated_at
-        return self.modified_at
+        return self.modified
diff --git a/webapp/prometheus_api/prometheus_handler.py b/webapp/prometheus_api/prometheus_handler.py
index 37cb0565..345ce1cd 100644
--- a/webapp/prometheus_api/prometheus_handler.py
+++ b/webapp/prometheus_api/prometheus_handler.py
@@ -43,6 +43,11 @@ def __init__(
     def get_metrics(self) -> str:
         sources = self.source_repository.fetch_sources()
 
+        last_modified_metrics = Metrics(
+            help='Last modification in seconds from now',
+            type=MetricType.gauge,
+            identifier='app_ocpdb_source_last_modified',
+        )
         last_static_update_metrics = Metrics(
             help='Last static update in seconds from now',
             type=MetricType.gauge,
@@ -77,6 +82,13 @@ def get_metrics(self) -> str:
             if source.static_status in [SourceStatus.DISABLED, SourceStatus.PROVISIONED]:
                 continue
 
+            last_modified_metrics.metrics.append(
+                SourceMetric(
+                    source=source.uid,
+                    value=int((datetime.now(tz=timezone.utc) - source.modified).total_seconds()),
+                )
+            )
+
             if source.static_data_updated_at:
                 last_static_update_metrics.metrics.append(
                     SourceMetric(
@@ -121,7 +133,8 @@ def get_metrics(self) -> str:
             )
 
         metrics = (
-            failed_static_sources.to_metrics()
+            last_modified_metrics.to_metrics()
+            + failed_static_sources.to_metrics()
             + last_static_update_metrics.to_metrics()
             + source_static_errors.to_metrics()
             + failed_realtime_sources.to_metrics()