diff --git a/data_source.go b/data_source.go
index 54f7e7c..b67f619 100644
--- a/data_source.go
+++ b/data_source.go
@@ -528,7 +528,12 @@ func (d *StructData) Get(field string) (val any, exist bool) {
 
 // TryGet value by field name. support get sub-value by path.
 func (d *StructData) TryGet(field string) (val any, exist, zero bool) {
-	field = strutil.UpperFirst(field)
+	// Only uppercase if the field is not already registered with its original casing.
+	// This allows private/unexported embedded struct fields to be accessed correctly
+	// when ValidatePrivateFields is enabled (e.g., "foo.Field1" must not become "Foo.Field1").
+	if _, ok := d.fieldNames[field]; !ok {
+		field = strutil.UpperFirst(field)
+	}
 	// try read from cache
 	if fv, ok := d.fieldValues[field]; ok {
 		return fv.Interface(), true, fv.IsZero()
@@ -632,7 +637,11 @@ func (d *StructData) TryGet(field string) (val any, exist, zero bool) {
 //
 // Notice: `StructData.src` the incoming struct must be a pointer to set the value
 func (d *StructData) Set(field string, val any) (newVal any, err error) {
-	field = strutil.UpperFirst(field)
+	// Only uppercase if the field is not already registered with its original casing.
+	// This mirrors the same fix in TryGet for private embedded struct fields.
+	if _, ok := d.fieldNames[field]; !ok {
+		field = strutil.UpperFirst(field)
+	}
 	if !d.HasField(field) { // field not found
 		return nil, ErrNoField
 	}
diff --git a/data_source_test.go b/data_source_test.go
index f3dc879..f07d065 100644
--- a/data_source_test.go
+++ b/data_source_test.go
@@ -270,23 +270,24 @@ func TestValidatePrivateFieldsWhenTrue(t *testing.T) {
 		Field2 int `validate:"required|int" message:"Field2 outside of range"`
 	}
 
-	fooInt := 4
-	barInt := 25
-
-	myFoo := foo{Field1: fooInt}
-	barz := &bar{
-		foo:    myFoo,
-		Field2: barInt,
-	}
-
 	Config(func(opt *GlobalOption) {
 		opt.ValidatePrivateFields = true
 	})
 
+	// Field1 = 4 violates min:5 — validation must fail for the right reason (rule violation)
+	barz := &bar{
+		foo:    foo{Field1: 4},
+		Field2: 25,
+	}
 	v := Struct(barz)
 	v.Validate()
-
 	assert.Equal(t, v.hasError, true)
+
+	// Field1 = 5 satisfies all rules — validation must pass
+	barz.foo.Field1 = 5
+	v = Struct(barz)
+	v.Validate()
+	assert.Equal(t, v.hasError, false)
 }
 
 func TestValidatePrivateFieldsWhenFalse(t *testing.T) {