diff --git a/core/internal/helpers/validation.go b/core/internal/helpers/validation.go
index 6d1fe8aa..8e21fa7a 100644
--- a/core/internal/helpers/validation.go
+++ b/core/internal/helpers/validation.go
@@ -31,12 +31,20 @@ func ValidateIP(ipaddr string) bool {
 // * Valid characters in a segment are letters, numbers, and dashes
 // * Segments may not start or end with a dash
 // * The exception is IPv6 addresses, which are also permitted.
+// * An underscore is allowed to support Docker Swarm service names.
 func ValidateHostname(hostname string) bool {
 	matches, _ := regexp.MatchString(`^([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])(\.([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9]))*$`, hostname)
+
 	if !matches {
-		// Try as an IP address
-		return ValidateIP(hostname)
+		// Try Docker Swarm service name
+		matchesDocker, _ := regexp.MatchString(`^([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])\_([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])$`, hostname)
+		if !matchesDocker {
+			// Try as an IP address
+			return ValidateIP(hostname)
+		}
+		return true
 	}
+
 	return matches
 }
 
diff --git a/core/internal/helpers/validation_test.go b/core/internal/helpers/validation_test.go
index 7fadd636..2f46eb22 100644
--- a/core/internal/helpers/validation_test.go
+++ b/core/internal/helpers/validation_test.go
@@ -11,8 +11,9 @@
 package helpers
 
 import (
-	"github.com/stretchr/testify/assert"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 type TestSet struct {
@@ -53,6 +54,12 @@ var testHostnames = []TestSet{
 	{"800.hostnames.starting.with.numbers.are.valid.because.people.suck.org", true},
 	{"hostnames-.may.not.end.with.a.dash.com", false},
 	{"no spaces.com", false},
+	{"docker_service.name.should.not.contain.dots", false},
+	{"docker-swarmservice_name-with-one-underscore-is-valid", true},
+	{"invalid-docker-_service-name", false},
+	{"invalid-docker_-service-name", false},
+	{"docker-service-may-not-end-with-underscore_", false},
+	{"_docker-service-may-not-start-with-underscore", false},
 }
 
 func TestValidateHostname(t *testing.T) {