diff --git a/go.mod b/go.mod
index c1a325a5ef90e0ae97a75951dc1b8ab8f4026f02..21dea2e117468766fe4d08928d77b74c4f39e141 100644
--- a/go.mod
+++ b/go.mod
@@ -7,7 +7,7 @@ require (
 	github.com/jhillyerd/enmime v0.8.3
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/oschwald/geoip2-golang v1.4.0
-	github.com/prometheus/client_golang v1.8.0
+	github.com/prometheus/client_golang v1.9.0
 	golang.org/x/sync 09787c993a3a
 	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 )