diff --git a/context.go b/context.go
index 8735bc5..110757a 100644
--- a/context.go
+++ b/context.go
@@ -36,5 +36,17 @@ func NewContext(locale ...string) *Context {
 func NewContextWithService(svc Translator, locale ...string) *Context {
 	ctx := NewContext(locale...)
 	ctx.service = svc
+	if len(locale) > 0 {
+		if setter, ok := svc.(interface{ SetLanguage(string) error }); ok {
+			base := locale[0]
+			for i := 0; i < len(base); i++ {
+				if base[i] == '-' || base[i] == '_' {
+					base = base[:i]
+					break
+				}
+			}
+			_ = setter.SetLanguage(base)
+		}
+	}
 	return ctx
 }
diff --git a/context_test.go b/context_test.go
index a9bedea..091785c 100644
--- a/context_test.go
+++ b/context_test.go
@@ -36,3 +36,13 @@ func TestNewContextWithService_OptionalLocale_Good(t *testing.T) {
 		t.Fatal("NewContextWithService should set translator service")
 	}
 }
+
+func TestNewContextWithService_AppliesLocaleToService_Good(t *testing.T) {
+	svc, _ := i18n.New()
+	ctx := NewContextWithService(svc, "fr-FR")
+
+	got := Text("prompt.yes").Render(ctx)
+	if got != "o" {
+		t.Fatalf("NewContextWithService locale translation = %q, want %q", got, "o")
+	}
+}