diff --git a/cmd/prometheus/limits_default.go b/cmd/prometheus/limits_default.go
index 06833065c..e2c6b10f6 100644
--- a/cmd/prometheus/limits_default.go
+++ b/cmd/prometheus/limits_default.go
@@ -39,7 +39,7 @@ func getLimits(resource int, unit string) string {
 	if err != nil {
 		log.Fatal("Error!")
 	}
-	return fmt.Sprintf("(soft=%s, hard=%s)", limitToString(rlimit.Cur, unit), limitToString(rlimit.Max, unit))
+	return fmt.Sprintf("(soft=%s, hard=%s)", limitToString(uint64(rlimit.Cur), unit), limitToString(uint64(rlimit.Max), unit))
 }
 
 // FdLimits returns the soft and hard limits for file descriptors.