diff --git a/CHANGELOG.md b/CHANGELOG.md
index 34c35c8..2281156 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,3 +2,9 @@
 
 Initial release : 
 - Creation of a `toJsonSupabase` which exclude the `primaryKey` from the `Map`
+
+## 0.0.4
+
+Only exclude `primaryKey` from the Map if :
+- Can't be nullable then check that `!= null`
+- The type is `String`, then check that the value `isNotEmpty`
\ No newline at end of file
diff --git a/README.md b/README.md
index 5c7cfe1..5b576d5 100644
--- a/README.md
+++ b/README.md
@@ -15,6 +15,10 @@ and the Flutter guide for
 Package greatly inspired by `JsonCodable` (from Dart), makes it easy to create 
 a JSON format of a template for Supabase.
 
+| Before                                                                                                                           | After                                                                                                                          |
+|----------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------|
+| ![before](https://raw.githubusercontent.com/ThomasDevApps/flutter_supabase_macro/flutter_supabase_macro_0.0.4/assets/before.png) | ![after](https://raw.githubusercontent.com/ThomasDevApps/flutter_supabase_macro/flutter_supabase_macro_0.0.4/assets/after.png) |
+
 - [What is a macro](#-what-is-a-macro)
 - [Getting started](#-getting-started)
 - [How it works](#-how-it-works)
@@ -62,15 +66,7 @@ class User {
   // ...
 }
 ```
-It will generate a `toJsonSupabase()` method that returns a 
-`Map<String, dynamic>` that does not contain the `primaryKey` 
-(`id` in this case) : 
-
-```dart
-final user = User(id: 'the-id', name: 'Toto', age: 22);
-final json = user.toJsonSupabase(); 
-print(json); // {'name': 'Toto', 'age': 22}
-```
+It will generate a `toJsonSupabase()` method that returns a `Map<String, dynamic>`.
 
 ## 📖 Additional information
 
diff --git a/assets/after.png b/assets/after.png
new file mode 100644
index 0000000..97ceb90
Binary files /dev/null and b/assets/after.png differ
diff --git a/assets/before.png b/assets/before.png
new file mode 100644
index 0000000..4f578b3
Binary files /dev/null and b/assets/before.png differ
diff --git a/lib/src/mixins/to_json_supabase.dart b/lib/src/mixins/to_json_supabase.dart
index fe147a2..b9bddf2 100644
--- a/lib/src/mixins/to_json_supabase.dart
+++ b/lib/src/mixins/to_json_supabase.dart
@@ -75,10 +75,8 @@ mixin _ToJsonSupabase on _Shared {
         superclassHasToJson: superclassHasToJson);
 
     // Get all fields
-    final fields = introspectionData.fields.where((f) {
-      bool canBeAdd = f.identifier.name != primaryKey;
-      return canBeAdd;
-    });
+    final fields = introspectionData.fields;
+    // Add entry for each fields
     parts.addAll(
       await Future.wait(
         fields.map(
@@ -86,6 +84,7 @@ mixin _ToJsonSupabase on _Shared {
             field,
             builder,
             introspectionData,
+            isPrimaryKey: field.identifier.name == primaryKey,
           ),
         ),
       ),
@@ -97,7 +96,8 @@ mixin _ToJsonSupabase on _Shared {
       docComments: CommentCode.fromParts([
         '  /// Map representing the model in json format for Supabase.\n',
         '  ///\n',
-        '  /// The `primaryKey` is exclude from the map.'
+        '  /// The primary key [${fields.first.identifier.name}]',
+        ' is exclude from the map if empty.'
       ]),
     );
   }
@@ -235,20 +235,38 @@ mixin _ToJsonSupabase on _Shared {
   ///   json[r'"age"'] = age!; // ! present only if the field is nullable by default.
   /// } // Only if the field is nullable.
   /// ```
+  ///
+  /// If `age` is a `String` and [isPrimaryKey] is true, then `age.isNotEmpty`
+  /// will be added in the definition of the condition.
   Future<Code> addEntryForField(
     FieldDeclaration field,
     DefinitionBuilder builder,
-    _SharedIntrospectionData introspectionData,
-  ) async {
+    _SharedIntrospectionData introspectionData, {
+    bool isPrimaryKey = false,
+  }) async {
     final parts = <Object>[];
     final doNullCheck = field.type.isNullable;
-    if (doNullCheck) {
-      parts.addAll([
-        'if (',
-        field.identifier,
-        ' != null) {\n      ',
-      ]);
+    final needCondition = doNullCheck || isPrimaryKey;
+    // Begin the definition of the condition
+    if (needCondition) {
+      parts.addAll(['if (']);
+    }
+    // Check that the field is not null
+    if (doNullCheck) parts.addAll([field.identifier, ' != null']);
+    // Check that the field is not empty (if String)
+    if (isPrimaryKey) {
+      final type = _checkNamedType(field.type, builder);
+      if (type != null) {
+        parts.addAll([
+          if (doNullCheck) ' && ',
+          if (type.identifier.name == 'String')
+            '${field.identifier.name}.isNotEmpty',
+        ]);
+      }
     }
+    // Close definition of the condition and open it
+    if (needCondition) parts.add(') {\n      ');
+    // Add the field in the json
     parts.addAll([
       "json[r'",
       field.identifier.name,
@@ -264,7 +282,8 @@ mixin _ToJsonSupabase on _Shared {
       ),
       ';\n    ',
     ]);
-    if (doNullCheck) {
+    // Close the condition
+    if (needCondition) {
       parts.add('}\n    ');
     }
     return RawCode.fromParts(parts);
diff --git a/pubspec.yaml b/pubspec.yaml
index 68fcc93..6e19d0e 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: flutter_supabase_macro
 description: "A new Flutter project."
-version: 0.0.3
+version: 0.0.4
 homepage:
 
 environment:
diff --git a/test/flutter_supabase_macro_test.dart b/test/flutter_supabase_macro_test.dart
index b00c3ec..b558d7e 100644
--- a/test/flutter_supabase_macro_test.dart
+++ b/test/flutter_supabase_macro_test.dart
@@ -11,12 +11,22 @@ class User {
 }
 
 void main() {
-  test('Test that id is missing from the json', () {
-    final user = User(id: 'id', name: 'Toto', age: 22);
+  test('Test that id is missing from the json because is empty', () {
+    final user = User(id: '', name: 'Toto', age: 22);
     final json = user.toJsonSupabase();
 
     expect(json.keys.length, 2);
     expect(json['name'], 'Toto');
     expect(json['age'], 22);
   });
+
+  test('Test that id is NOT missing from the json because is NOT empty', () {
+    final user = User(id: 'id-123', name: 'Toto', age: 22);
+    final json = user.toJsonSupabase();
+
+    expect(json.keys.length, 3);
+    expect(json['id'], 'id-123');
+    expect(json['name'], 'Toto');
+    expect(json['age'], 22);
+  });
 }