diff --git a/cmd/prometheus/config.go b/cmd/prometheus/config.go
index 9e0f2eca1..879210827 100644
--- a/cmd/prometheus/config.go
+++ b/cmd/prometheus/config.go
@@ -262,6 +262,10 @@ func parse(args []string) error {
 		return err
 	}
 
+	if promql.StalenessDelta < 0 {
+		return fmt.Errorf("negative staleness delta: %s", promql.StalenessDelta)
+	}
+
 	if err := parsePrometheusURL(); err != nil {
 		return err
 	}