diff --git a/_testdata/positive/servers.json b/_testdata/positive/servers.json
index 5aff6bbbc..e8124268c 100644
--- a/_testdata/positive/servers.json
+++ b/_testdata/positive/servers.json
@@ -38,6 +38,15 @@
     {
       "x-ogen-server-name": "const",
       "url": "https://cdn.example.com/v1"
+    },
+    {
+      "x-ogen-server-name": "optionalVars",
+      "url": "https://cdn.example.com/{version}",
+      "variables": {
+        "version": {
+          "default": "v1"
+        }
+      }
     }
   ],
   "info": {
diff --git a/gen/_template/servers.tmpl b/gen/_template/servers.tmpl
index d18bf16ed..dc40ad488 100644
--- a/gen/_template/servers.tmpl
+++ b/gen/_template/servers.tmpl
@@ -50,6 +50,7 @@ func (s {{ $s.Name }}) Build() (string, error) {
 	}
 	{{- range $p := $s.Params }}
 	s.{{ $p.Name }} = zeroOr(s.{{ $p.Name }}, {{ quote $p.Spec.Default }})
+	{{- if $p.Spec.Enum }}
 	// Validate {{ quote $p.Spec.Name }}
 	switch s.{{ $p.Name }} {
 	{{- range $e := $p.Spec.Enum }}
@@ -59,6 +60,7 @@ func (s {{ $s.Name }}) Build() (string, error) {
 		return "", errors.Errorf("param %q: unexpected value %q", {{ quote $p.Spec.Name }}, s.{{ $p.Name }})
 	}
 	{{- end }}
+	{{- end }}
 	return fmt.Sprintf({{ $s.FormatString | quote }},
 		{{- range $p := $s.Params }}
 		s.{{ $p.Name }},
diff --git a/internal/integration/test_servers/oas_servers_gen.go b/internal/integration/test_servers/oas_servers_gen.go
index 5e38188c8..6e389156d 100644
--- a/internal/integration/test_servers/oas_servers_gen.go
+++ b/internal/integration/test_servers/oas_servers_gen.go
@@ -129,6 +129,53 @@ func (s PrefixServer) Build() (string, error) {
 	), nil
 }
 
+// OptionalVarsServer is a server URL template.
+type OptionalVarsServer struct {
+	Version string `json:"version" yaml:"version"`
+}
+
+// MustPath returns the computed path. It panics if any error occurs.
+func (s OptionalVarsServer) MustPath() string {
+	return errors.Must(s.Path())
+}
+
+// Path returns the computed path.
+func (s OptionalVarsServer) Path() (string, error) {
+	raw, err := s.Build()
+	if err != nil {
+		return "", err
+	}
+	u, err := url.Parse(raw)
+	if err != nil {
+		return "", err
+	}
+	return u.Path, nil
+}
+
+// MustBuild returns the computed server URL. It panics if any error occurs.
+func (s OptionalVarsServer) MustBuild() string {
+	return errors.Must(s.Build())
+}
+
+// Build returns the computed server URL.
+//
+// If variable is empty, it uses the default value.
+// If spec defines an enum and given value is not in the enum, it returns an error.
+//
+// Notice that given values will not be escaped and may cause invalid URL.
+func (s OptionalVarsServer) Build() (string, error) {
+	zeroOr := func(s string, def string) string {
+		if s == "" {
+			return def
+		}
+		return s
+	}
+	s.Version = zeroOr(s.Version, "v1")
+	return fmt.Sprintf("https://cdn.example.com/%s",
+		s.Version,
+	), nil
+}
+
 type serverConst string
 
 // MustPath returns the computed path. It panics if any error occurs.