diff --git a/go.mod b/go.mod
index 43e61ad..662b9e9 100644
--- a/go.mod
+++ b/go.mod
@@ -4,7 +4,7 @@ go 1.18
 
 require (
 	fortio.org/cli v1.4.2
-	fortio.org/dflag v1.5.3
+	fortio.org/dflag v1.6.0
 	fortio.org/log v1.11.0
 	fortio.org/version v1.0.3
 	golang.org/x/sys v0.13.0
@@ -13,5 +13,5 @@ require (
 require (
 	fortio.org/sets v1.0.3 // indirect
 	github.com/fsnotify/fsnotify v1.6.0 // indirect
-	golang.org/x/exp v0.0.0-20230801115018-d63ba01acd4b // indirect
+	golang.org/x/exp v0.0.0-20231006140011-7918f672742d // indirect
 )
diff --git a/go.sum b/go.sum
index 6df0a5a..b663001 100644
--- a/go.sum
+++ b/go.sum
@@ -1,8 +1,8 @@
 fortio.org/assert v1.2.0 h1:XscfvR8yp4xW7OMCvNbCsieRFDxlwdEcb69+JZRp6LA=
 fortio.org/cli v1.4.2 h1:pCYVPk5FpQuJtD31f9CG8sdgoTOWdv9Gls8As/MLJhU=
 fortio.org/cli v1.4.2/go.mod h1:VGqFDEKpA6u3NbTM3aSz2lZfAYKnGaszl1pLxbBhxsY=
-fortio.org/dflag v1.5.3 h1:+pCqZBCz95PYTxhcmenjrkVORWIRB1Je4eO/So574Bc=
-fortio.org/dflag v1.5.3/go.mod h1:cM/ojIzdDv8FRA5yqSRpDK9jCGmASln0k7ag3zeiqbw=
+fortio.org/dflag v1.6.0 h1:acOc3KAu1kgp3Ov1nT2GbmcuNhPF1oMZqhT9nj3Oz1U=
+fortio.org/dflag v1.6.0/go.mod h1:MeDNYnBh30L6OdMGgAL6ltDX2xdQjOiexCZYPYXH8uM=
 fortio.org/log v1.11.0 h1:w7ueGPGbXz0A3+ApMz/5Q9gwEMrwSo/ohTlLo2Um6dU=
 fortio.org/log v1.11.0/go.mod h1:u/8/2lyczXq52aT5Nw6reD+3cR6m/EbS2jBiIYhgiTU=
 fortio.org/sets v1.0.3 h1:HzewdGjH69YmyW06yzplL35lGr+X4OcqQt0qS6jbaO4=
@@ -11,8 +11,8 @@ fortio.org/version v1.0.3 h1:5gJ3plj6isAOMq52cI5ifo4cC+QHmJF76Wevc5Cp4x0=
 fortio.org/version v1.0.3/go.mod h1:2JQp9Ax+tm6QKiGuzR5nJY63kFeANcgrZ0osoQFDVm0=
 github.com/fsnotify/fsnotify v1.6.0 h1:n+5WquG0fcWoWp6xPWfHdbskMCQaFnG6PfBrh1Ky4HY=
 github.com/fsnotify/fsnotify v1.6.0/go.mod h1:sl3t1tCWJFWoRz9R8WJCbQihKKwmorjAbSClcnxKAGw=
-golang.org/x/exp v0.0.0-20230801115018-d63ba01acd4b h1:r+vk0EmXNmekl0S0BascoeeoHk/L7wmaW2QF90K+kYI=
-golang.org/x/exp v0.0.0-20230801115018-d63ba01acd4b/go.mod h1:FXUEEKJgO7OQYeo8N01OfiKP8RXMtf6e8aTskBGqWdc=
+golang.org/x/exp v0.0.0-20231006140011-7918f672742d h1:jtJma62tbqLibJ5sFQz8bKtEM8rJBtfilJ2qTU199MI=
+golang.org/x/exp v0.0.0-20231006140011-7918f672742d/go.mod h1:ldy0pHrwJyGW56pPQzzkH36rKxoZW1tw7ZJpeKx+hdo=
 golang.org/x/sys v0.0.0-20220908164124-27713097b956/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
 golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
diff --git a/scli.go b/scli.go
index 43662b7..c2244e4 100644
--- a/scli.go
+++ b/scli.go
@@ -31,6 +31,8 @@ import (
 	"fortio.org/version"
 )
 
+var ConfigMapUpdater *configmap.Updater // Expose the updater if advanced callers want to check warnings or stop it etc.
+
 // NormalizePort parses port and returns host:port if port is in the form
 // of host:port already or :port if port is only a port (doesn't contain :).
 // Copied from fortio.org/fnet.NormalizePort to avoid dependency loop.
@@ -76,8 +78,12 @@ func ServerMain() bool {
 	cli.ServerMode = true
 	cli.Main() // will call ExitFunction() if there are usage errors
 	if *configDir != "" {
-		if _, err := configmap.Setup(flag.CommandLine, *configDir); err != nil {
+		var err error
+		ConfigMapUpdater, err = configmap.Setup(flag.CommandLine, *configDir)
+		if err != nil {
 			log.Critf("Unable to watch config/flag changes in %v: %v", *configDir, err)
+		} else if ConfigMapUpdater.Warnings() != 0 {
+			log.S(log.Warning, "Unknown flags found", log.Int("count", ConfigMapUpdater.Warnings()), log.Str("dir", *configDir))
 		}
 	}