diff --git a/go.mod b/go.mod
index b840bed..8a72244 100644
--- a/go.mod
+++ b/go.mod
@@ -3,7 +3,7 @@ module github.com/decke/smtprelay
 require (
 	github.com/chrj/smtpd v0.3.1
 	github.com/google/uuid v1.3.0
-	github.com/peterbourgon/ff/v3 v3.3.2
+	github.com/peterbourgon/ff/v3 v3.4.0
 	github.com/sirupsen/logrus v1.9.3
 	github.com/stretchr/testify v1.8.4
 	golang.org/x/crypto v0.11.0
diff --git a/go.sum b/go.sum
index cdc7791..aba89dc 100644
--- a/go.sum
+++ b/go.sum
@@ -13,8 +13,8 @@ github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
-github.com/peterbourgon/ff/v3 v3.3.2 h1:2J07/5/36kd9HYVt42Zve0xCeQ+LLRIvoKrt6sAZXJ4=
-github.com/peterbourgon/ff/v3 v3.3.2/go.mod h1:zjJVUhx+twciwfDl0zBcFzl4dW8axCRyXE/eKY9RztQ=
+github.com/peterbourgon/ff/v3 v3.4.0 h1:QBvM/rizZM1cB0p0lGMdmR7HxZeI/ZrBWB4DqLkMUBc=
+github.com/peterbourgon/ff/v3 v3.4.0/go.mod h1:zjJVUhx+twciwfDl0zBcFzl4dW8axCRyXE/eKY9RztQ=
 github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsKMEsNbx1VGcRFpLqf3715MtcvvzbA=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=