diff --git a/internal/cortex/querier/queryrange/results_cache.go b/internal/cortex/querier/queryrange/results_cache.go
index c32abba8ace..b54224520f6 100644
--- a/internal/cortex/querier/queryrange/results_cache.go
+++ b/internal/cortex/querier/queryrange/results_cache.go
@@ -516,6 +516,15 @@ func (s resultsCache) handleHit(ctx context.Context, r Request, extents []Extent
 	}
 
 	response, err := s.merger.MergeResponse(r, responses...)
+	if err == nil {
+		if promResp, ok := response.(*PrometheusResponse); ok {
+			promResp.Headers = append(promResp.Headers, &PrometheusResponseHeader{
+				Name:   "X-Thanos-Results-Cache",
+				Values: []string{fmt.Sprintf("hit; extents=%d", len(extents))},
+			})
+		}
+	}
+
 	return response, mergedExtents, err
 }