diff --git a/proto/src/metrics_constants.proto b/proto/src/metrics_constants.proto
index 0cc60e3146d78..b3ec8d022d080 100644
--- a/proto/src/metrics_constants.proto
+++ b/proto/src/metrics_constants.proto
@@ -3964,7 +3964,8 @@ message MetricsEvent {
     // Type TYPE_FAILURE: The request failed
     // Package: Package of app that is autofilled
     // Tag FIELD_AUTOFILL_SERVICE: Package of service that processed the request
-    // Tag FIELD_AUTOFILL_NUM_DATASETS: The number of datasets returned (only in success case)
+    // Tag FIELD_AUTOFILL_NUM_DATASETS: The number of datasets returned in the response, or -1 if
+    // the service returned a null response.
     // NOTE: starting on OS P, it also added:
     // Type TYPE_CLOSE: Service returned a null response.
     // Tag FIELD_AUTOFILL_NUM_FIELD_CLASSIFICATION_IDS: if service requested field classification,
diff --git a/services/autofill/java/com/android/server/autofill/Session.java b/services/autofill/java/com/android/server/autofill/Session.java
index 7f57615163022..55c0372dc3a03 100644
--- a/services/autofill/java/com/android/server/autofill/Session.java
+++ b/services/autofill/java/com/android/server/autofill/Session.java
@@ -596,6 +596,9 @@ final class Session implements RemoteFillService.FillServiceCallbacks, ViewState
             }
             if (response == null) {
                 processNullResponseLocked(requestFlags);
+                mMetricsLogger.write(newLogMaker(MetricsEvent.AUTOFILL_REQUEST, servicePackageName)
+                        .setType(MetricsEvent.TYPE_SUCCESS)
+                        .addTaggedData(MetricsEvent.FIELD_AUTOFILL_NUM_DATASETS, -1));
                 return;
             }