diff --git a/go.mod b/go.mod
index f22c264bd..6982fa83c 100644
--- a/go.mod
+++ b/go.mod
@@ -58,6 +58,7 @@ require (
 	github.com/onsi/gomega v1.4.3 // indirect
 	github.com/op/go-logging v0.0.0-20160315200505-970db520ece7
 	github.com/pelletier/go-toml v1.4.0 // indirect
+	github.com/pkg/errors v0.8.1 // indirect
 	github.com/prometheus/client_golang v0.9.2
 	github.com/samedi/caldav-go v3.0.0+incompatible
 	github.com/shurcooL/httpfs v0.0.0-20190527155220-6a4d4a70508b
@@ -78,7 +79,6 @@ require (
 	golang.org/x/tools v0.0.0-20191130070609-6e064ea0cf2d // indirect
 	google.golang.org/appengine v1.5.0 // indirect
 	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
-	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 	gopkg.in/d4l3k/messagediff.v1 v1.2.1
 	gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df
 	gopkg.in/testfixtures.v2 v2.5.3
diff --git a/go.sum b/go.sum
index f591dffc1..55e9e039c 100644
--- a/go.sum
+++ b/go.sum
@@ -360,8 +360,6 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
-gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/d4l3k/messagediff.v1 v1.2.1 h1:70AthpjunwzUiarMHyED52mj9UwtAnE89l1Gmrt3EU0=
 gopkg.in/d4l3k/messagediff.v1 v1.2.1/go.mod h1:EUzikiKadqXWcD1AzJLagx0j/BeeWGtn++04Xniyg44=
 gopkg.in/fsnotify.v1 v1.4.7 h1:xOHLXZwVvI9hhs+cLKq5+I5onOuwQLhQwiu63xxlHs4=