diff --git a/tests/time_tracker_api/api_test.py b/tests/time_tracker_api/api_test.py
index a9af25da..6f9ad353 100644
--- a/tests/time_tracker_api/api_test.py
+++ b/tests/time_tracker_api/api_test.py
@@ -22,3 +22,24 @@ def test_create_attributes_filter_with_valid_attribute_should_succeed():
 
     assert filter is not None
     assert type(filter) is RequestParser
+
+
+def test_remove_required_constraint():
+    from time_tracker_api.api import remove_required_constraint
+    from flask_restplus import fields
+    from flask_restplus import Namespace
+
+    ns = Namespace('todos', description='Namespace for testing')
+    sample_model = ns.model('Todo', {
+        'id': fields.Integer(readonly=True, description='The task unique identifier'),
+        'task': fields.String(required=True, description='The task details'),
+        'done': fields.Boolean(required=False, description='Has it being done or not')
+    })
+
+    new_model = remove_required_constraint(sample_model)
+
+    assert new_model is not sample_model
+
+    for attrib in sample_model:
+        assert new_model[attrib].required is False, "No attribute should be required"
+        assert new_model[attrib] is not sample_model[attrib], "No attribute should be required"
diff --git a/time_tracker_api/__init__.py b/time_tracker_api/__init__.py
index 848a01ac..b23a3c6b 100644
--- a/time_tracker_api/__init__.py
+++ b/time_tracker_api/__init__.py
@@ -38,8 +38,8 @@ def init_app(app: Flask):
     from commons.data_access_layer.database import init_app as init_database
     init_database(app)
 
-    from time_tracker_api.api import api
-    api.init_app(app)
+    from time_tracker_api.api import init_app
+    init_app(app)
 
     if app.config.get('DEBUG'):
         app.logger.setLevel(logging.INFO)
diff --git a/time_tracker_api/activities/activities_namespace.py b/time_tracker_api/activities/activities_namespace.py
index ba783bc2..1dffc3dc 100644
--- a/time_tracker_api/activities/activities_namespace.py
+++ b/time_tracker_api/activities/activities_namespace.py
@@ -3,7 +3,7 @@
 from flask_restplus._http import HTTPStatus
 
 from time_tracker_api.activities.activities_model import create_dao
-from time_tracker_api.api import common_fields, api
+from time_tracker_api.api import common_fields, api, remove_required_constraint
 
 faker = Faker()
 
@@ -68,7 +68,7 @@ def get(self, id):
         return activity_dao.get(id)
 
     @ns.doc('update_activity')
-    @ns.expect(activity_input)
+    @ns.expect(remove_required_constraint(activity_input))
     @ns.response(HTTPStatus.BAD_REQUEST, 'Invalid format or structure of the activity')
     @ns.response(HTTPStatus.CONFLICT, 'An activity already exists with this new data')
     @ns.marshal_with(activity)
diff --git a/time_tracker_api/api.py b/time_tracker_api/api.py
index 089a04d6..59b8b3cd 100644
--- a/time_tracker_api/api.py
+++ b/time_tracker_api/api.py
@@ -1,6 +1,6 @@
 from azure.cosmos.exceptions import CosmosResourceExistsError, CosmosResourceNotFoundError, CosmosHttpResponseError
 from faker import Faker
-from flask import current_app as app
+from flask import current_app as app, Flask
 from flask_restplus import Api, fields, Model
 from flask_restplus import namespace
 from flask_restplus._http import HTTPStatus
@@ -22,7 +22,14 @@
 )
 
 
-# Filters
+def remove_required_constraint(model: Model):
+    result = model.resolved
+    for attrib in result:
+        result[attrib].required = False
+
+    return result
+
+
 def create_attributes_filter(ns: namespace, model: Model, filter_attrib_names: list) -> RequestParser:
     attribs_parser = ns.parser()
     model_attributes = model.resolved
@@ -72,26 +79,30 @@ def __init__(self, *args, **kwargs):
     ),
 }
 
-# APIs
-from time_tracker_api.projects import projects_namespace
 
-api.add_namespace(projects_namespace.ns)
+def init_app(app: Flask):
+    api.init_app(app)
+
+    from time_tracker_api.projects import projects_namespace
+
+    api.add_namespace(projects_namespace.ns)
+
+    from time_tracker_api.activities import activities_namespace
 
-from time_tracker_api.activities import activities_namespace
+    api.add_namespace(activities_namespace.ns)
 
-api.add_namespace(activities_namespace.ns)
+    from time_tracker_api.time_entries import time_entries_namespace
 
-from time_tracker_api.time_entries import time_entries_namespace
+    api.add_namespace(time_entries_namespace.ns)
 
-api.add_namespace(time_entries_namespace.ns)
+    from time_tracker_api.project_types import project_types_namespace
 
-from time_tracker_api.project_types import project_types_namespace
+    api.add_namespace(project_types_namespace.ns)
 
-api.add_namespace(project_types_namespace.ns)
+    from time_tracker_api.customers import customers_namespace
 
-from time_tracker_api.customers import customers_namespace
+    api.add_namespace(customers_namespace.ns)
 
-api.add_namespace(customers_namespace.ns)
 
 """
 Error handlers
diff --git a/time_tracker_api/customers/customers_namespace.py b/time_tracker_api/customers/customers_namespace.py
index f455cb22..d38f4566 100644
--- a/time_tracker_api/customers/customers_namespace.py
+++ b/time_tracker_api/customers/customers_namespace.py
@@ -2,7 +2,7 @@
 from flask_restplus import Resource, fields
 from flask_restplus._http import HTTPStatus
 
-from time_tracker_api.api import common_fields, api
+from time_tracker_api.api import common_fields, api, remove_required_constraint
 from time_tracker_api.customers.customers_model import create_dao
 
 faker = Faker()
@@ -74,7 +74,7 @@ def get(self, id):
     @ns.response(HTTPStatus.BAD_REQUEST, 'Invalid format or structure '
                                          'of the attributes of the customer')
     @ns.response(HTTPStatus.CONFLICT, 'A customer already exists with this new data')
-    @ns.expect(customer_input)
+    @ns.expect(remove_required_constraint(customer_input))
     @ns.marshal_with(customer)
     def put(self, id):
         """Update a customer"""
diff --git a/time_tracker_api/project_types/project_types_namespace.py b/time_tracker_api/project_types/project_types_namespace.py
index 8e1e759e..7d717b7f 100644
--- a/time_tracker_api/project_types/project_types_namespace.py
+++ b/time_tracker_api/project_types/project_types_namespace.py
@@ -2,7 +2,7 @@
 from flask_restplus import Resource, fields
 from flask_restplus._http import HTTPStatus
 
-from time_tracker_api.api import common_fields, create_attributes_filter, api, UUID
+from time_tracker_api.api import common_fields, create_attributes_filter, api, UUID, remove_required_constraint
 from time_tracker_api.project_types.project_types_model import create_dao
 
 faker = Faker()
@@ -94,7 +94,7 @@ def get(self, id):
     @ns.response(HTTPStatus.BAD_REQUEST, 'Invalid format or structure '
                                          'of the attributes of the project type')
     @ns.response(HTTPStatus.CONFLICT, 'A project type already exists with this new data')
-    @ns.expect(project_type_input)
+    @ns.expect(remove_required_constraint(project_type_input))
     @ns.marshal_with(project_type)
     def put(self, id):
         """Update a project type"""
diff --git a/time_tracker_api/projects/projects_namespace.py b/time_tracker_api/projects/projects_namespace.py
index 634af17e..9c39e53e 100644
--- a/time_tracker_api/projects/projects_namespace.py
+++ b/time_tracker_api/projects/projects_namespace.py
@@ -2,7 +2,7 @@
 from flask_restplus import Resource, fields
 from flask_restplus._http import HTTPStatus
 
-from time_tracker_api.api import common_fields, create_attributes_filter, UUID, api
+from time_tracker_api.api import common_fields, create_attributes_filter, UUID, api, remove_required_constraint
 from time_tracker_api.projects.projects_model import create_dao
 
 faker = Faker()
@@ -94,7 +94,7 @@ def get(self, id):
     @ns.response(HTTPStatus.BAD_REQUEST, 'Invalid format or structure '
                                          'of the attributes of the project')
     @ns.response(HTTPStatus.CONFLICT, 'A project already exists with this new data')
-    @ns.expect(project_input)
+    @ns.expect(remove_required_constraint(project_input))
     @ns.marshal_with(project)
     def put(self, id):
         """Update a project"""
diff --git a/time_tracker_api/time_entries/time_entries_namespace.py b/time_tracker_api/time_entries/time_entries_namespace.py
index 87ba7f46..9df422a4 100644
--- a/time_tracker_api/time_entries/time_entries_namespace.py
+++ b/time_tracker_api/time_entries/time_entries_namespace.py
@@ -6,7 +6,8 @@
 
 from commons.data_access_layer.cosmos_db import current_datetime, datetime_str, current_datetime_str
 from commons.data_access_layer.database import COMMENTS_MAX_LENGTH
-from time_tracker_api.api import common_fields, create_attributes_filter, api, UUID
+from time_tracker_api.api import common_fields, create_attributes_filter, api, UUID, NullableString, \
+    remove_required_constraint
 from time_tracker_api.time_entries.time_entries_model import create_dao
 
 faker = Faker()
@@ -48,7 +49,7 @@
         description='When the user ended doing this activity',
         example=current_datetime_str(),
     ),
-    'uri': fields.String(
+    'uri': NullableString(
         title='Uniform Resource identifier',
         description='Either identifier or locator of a resource in the Internet that helps to understand'
                     ' what this time entry was about. For example, A Jira ticket, a Github issue, a Google document.',
@@ -146,7 +147,7 @@ def get(self, id):
                                          'of the attributes of the time entry')
     @ns.response(HTTPStatus.CONFLICT, 'A time entry already exists with this new data or there'
                                       ' is a bad reference for the project or activity')
-    @ns.expect(time_entry_input)
+    @ns.expect(remove_required_constraint(time_entry_input))
     @ns.marshal_with(time_entry)
     def put(self, id):
         """Update a time entry"""