diff --git a/core/mapping/unmarshaler.go b/core/mapping/unmarshaler.go
index f68748c6..8bc2fed1 100644
--- a/core/mapping/unmarshaler.go
+++ b/core/mapping/unmarshaler.go
@@ -919,12 +919,16 @@ func (u *Unmarshaler) processNamedFieldWithoutValue(fieldType reflect.Type, valu
 	}
 
 	switch fieldKind {
-	case reflect.Array, reflect.Map, reflect.Slice:
+	case reflect.Array, reflect.Slice:
 		if !opts.optional() {
 			return u.processFieldNotFromString(fieldType, value, valueWithParent{
 				value: emptyMap,
 			}, opts, fullName)
 		}
+	case reflect.Map:
+		if !opts.optional() {
+			return newInitError(fullName)
+		}
 	case reflect.Struct:
 		if !opts.optional() {
 			required, err := structValueRequired(u.key, derefedType)
diff --git a/core/mapping/unmarshaler_test.go b/core/mapping/unmarshaler_test.go
index ae2aba0e..c281eb01 100644
--- a/core/mapping/unmarshaler_test.go
+++ b/core/mapping/unmarshaler_test.go
@@ -2432,6 +2432,42 @@ func TestUnmarshalMapOfStruct(t *testing.T) {
 		}
 		assert.Error(t, UnmarshalKey(m, &v))
 	})
+
+	t.Run("map set", func(t *testing.T) {
+		type Inner1 struct {
+			M map[string]string
+		}
+		assert.Error(t, UnmarshalKey(map[string]any{}, &Inner1{}))
+		assert.NoError(t, UnmarshalKey(map[string]any{
+			"M": map[string]string{},
+		}, &Inner1{}))
+
+		type Inner2 struct {
+			Inner1
+		}
+		assert.Error(t, UnmarshalKey(map[string]any{}, &Inner2{}))
+		assert.NoError(t, UnmarshalKey(map[string]any{
+			"M": map[string]string{},
+		}, &Inner2{}))
+
+		type Inner3 struct {
+			C Inner1
+		}
+		assert.Error(t, UnmarshalKey(map[string]any{}, &Inner3{}))
+		assert.NoError(t, UnmarshalKey(map[string]any{
+			"C": map[string]any{
+				"M": map[string]string{},
+			},
+		}, &Inner3{}))
+
+		type Inner4 struct {
+			M map[string]string `json:",optional"`
+		}
+		assert.NoError(t, UnmarshalKey(map[string]any{}, &Inner4{}))
+		assert.NoError(t, UnmarshalKey(map[string]any{
+			"M": map[string]string{},
+		}, &Inner4{}))
+	})
 }
 
 func TestUnmarshalSlice(t *testing.T) {