diff --git a/daemon/config/config.go b/daemon/config/config.go
index f82fd23768..77bd3f49f5 100644
--- a/daemon/config/config.go
+++ b/daemon/config/config.go
@@ -76,12 +76,13 @@ var builtinRuntimes = map[string]bool{
 // Use this to differentiate these options
 // with others like the ones in TLSOptions.
 var flatOptions = map[string]bool{
-	"cluster-store-opts": true,
-	"log-opts":           true,
-	"runtimes":           true,
-	"default-ulimits":    true,
-	"features":           true,
-	"builder":            true,
+	"cluster-store-opts":   true,
+	"default-network-opts": true,
+	"log-opts":             true,
+	"runtimes":             true,
+	"default-ulimits":      true,
+	"features":             true,
+	"builder":              true,
 }
 
 // skipValidateOptions contains configuration keys
diff --git a/daemon/config/config_linux_test.go b/daemon/config/config_linux_test.go
index 26c2a9ea05..9333ae64df 100644
--- a/daemon/config/config_linux_test.go
+++ b/daemon/config/config_linux_test.go
@@ -25,6 +25,11 @@ func TestGetConflictFreeConfiguration(t *testing.T) {
 			},
 			"log-opts": {
 				"tag": "test_tag"
+			},
+			"default-network-opts": {
+				"overlay": {
+					"com.docker.network.driver.mtu": "1337"
+				}
 			}
 		}`)
 
@@ -33,6 +38,7 @@ func TestGetConflictFreeConfiguration(t *testing.T) {
 	flags.BoolVarP(&debug, "debug", "D", false, "")
 	flags.Var(opts.NewNamedUlimitOpt("default-ulimits", nil), "default-ulimit", "")
 	flags.Var(opts.NewNamedMapOpts("log-opts", nil, nil), "log-opt", "")
+	flags.Var(opts.NewNamedMapMapOpts("default-network-opts", nil, nil), "default-network-opt", "")
 
 	cc, err := getConflictFreeConfiguration(configFile, flags)
 	assert.NilError(t, err)