diff --git a/modules/project_invoice/invoice.py b/modules/project_invoice/invoice.py
index 0fc5b547fe..769adb99b9 100644
--- a/modules/project_invoice/invoice.py
+++ b/modules/project_invoice/invoice.py
@@ -1,13 +1,114 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
+
+import datetime as dt
+
+from sql.aggregate import Sum
+
+from trytond.i18n import gettext
+from trytond.model import fields
+from trytond.modules.account_invoice.exceptions import (
+    InvoiceLineValidationError)
 from trytond.pool import Pool, PoolMeta
-from trytond.tools import grouped_slice
+from trytond.tools import grouped_slice, reduce_ids
 from trytond.transaction import Transaction
 
 
 class InvoiceLine(metaclass=PoolMeta):
     __name__ = 'account.invoice.line'
 
+    project_invoice_works = fields.One2Many(
+        'project.work', 'invoice_line',
+        "Project Invoice Works", readonly=True)
+    project_invoice_progresses = fields.One2Many(
+        'project.work.invoiced_progress', 'invoice_line',
+        "Project Invoice Progresses", readonly=True)
+    project_invoice_timesheet_duration = fields.Function(
+        fields.TimeDelta("Project Invoice Timesheet Duration"),
+        'get_project_invoice_timesheet_duration')
+
+    @classmethod
+    def check_validate_project_invoice_quantity(cls, lines, field_names):
+        pool = Pool()
+        Lang = pool.get('ir.lang')
+        if field_names and not (field_names & {
+                    'quantity', 'project_invoice_works'}):
+            return
+        for line in lines:
+            project_invoice_quantity = line.project_invoice_quantity
+            if project_invoice_quantity is None:
+                continue
+            if line.unit:
+                project_invoice_quantity = line.unit.round(
+                    project_invoice_quantity)
+            if line.quantity != project_invoice_quantity:
+                lang = Lang.get()
+                if line.unit:
+                    quantity = lang.format_number_symbol(
+                        project_invoice_quantity, line.unit)
+                else:
+                    quantity = lang.format_number(project_invoice_quantity)
+                raise InvoiceLineValidationError(gettext(
+                        'project_invoice.msg_project_invoice_line_quantity',
+                        invoice_line=line.rec_name,
+                        quantity=quantity,
+                        ))
+
+    @property
+    def project_invoice_quantity(self):
+        quantity = None
+        for work in self.project_invoice_works:
+            if quantity is None:
+                quantity = 0
+            if work.price_list_hour:
+                quantity += work.effort_hours
+            else:
+                quantity += 1
+        for progress in self.project_invoice_progresses:
+            if quantity is None:
+                quantity = 0
+            work = progress.work
+            if work.price_list_hour:
+                quantity += progress.progress * work.effort_hours
+            else:
+                quantity += progress.progress
+        if self.project_invoice_timesheet_duration is not None:
+            if quantity is None:
+                quantity = 0
+            quantity += (
+                self.project_invoice_timesheet_duration.total_seconds()
+                / 60 / 60)
+        return quantity
+
+    @classmethod
+    def get_project_invoice_timesheet_duration(cls, lines, name):
+        pool = Pool()
+        TimesheetLine = pool.get('timesheet.line')
+        cursor = Transaction().connection.cursor()
+        ts_line = TimesheetLine.__table__()
+
+        durations = dict.fromkeys(map(int, lines))
+        query = ts_line.select(
+            ts_line.invoice_line, Sum(ts_line.duration),
+            group_by=ts_line.invoice_line)
+        for sub_lines in grouped_slice(lines):
+            query.where = reduce_ids(
+                ts_line.invoice_line, map(int, sub_lines))
+            cursor.execute(*query)
+
+            for line_id, duration in cursor:
+                # SQLite uses float for SUM
+                if (duration is not None
+                        and not isinstance(duration, dt.timedelta)):
+                    duration = dt.timedelta(seconds=duration)
+                durations[line_id] = duration
+        return durations
+
+    @classmethod
+    def validate_fields(cls, lines, field_names):
+        super().validate_fields(lines, field_names)
+        cls.check_validate_project_invoice_quantity(lines, field_names)
+
     @classmethod
     def delete(cls, lines):
         pool = Pool()
diff --git a/modules/project_invoice/message.xml b/modules/project_invoice/message.xml
index 524ee4be69..14f7feef9c 100644
--- a/modules/project_invoice/message.xml
+++ b/modules/project_invoice/message.xml
@@ -30,5 +30,8 @@ this repository contains the full copyright notices and license terms. -->
         <record model="ir.message" id="msg_invoiced_work_delete">
             <field name="text">You cannot delete work "%(work)s" because it has been invoiced.</field>
         </record>
+        <record model="ir.message" id="msg_project_invoice_line_quantity">
+            <field name="text">The quantity of project invoice line "%(invoice_line)s" must be "%(quantity)s"</field>
+        </record>
     </data>
 </tryton>
diff --git a/modules/project_invoice/tests/scenario_project_invoice_effort.rst b/modules/project_invoice/tests/scenario_project_invoice_effort.rst
index c0fd8c8860..ddad0e454d 100644
--- a/modules/project_invoice/tests/scenario_project_invoice_effort.rst
+++ b/modules/project_invoice/tests/scenario_project_invoice_effort.rst
@@ -192,3 +192,16 @@ Invoice again project::
     Decimal('0.00')
     >>> project.invoiced_amount
     Decimal('170.00')
+
+Try to change invoice line quantity::
+
+    >>> set_user(1)
+    >>> ProjectWork = Model.get('project.work')
+    >>> task = ProjectWork(task.id)
+    >>> task.invoice_line.quantity = 1
+    >>> task.invoice_line.save()  # doctest: +IGNORE_EXCEPTION_DETAIL
+    Traceback (most recent call last):
+        ...
+    InvoiceLineValidationError: ...
+    >>> task.invoice_line.quantity = 5
+    >>> task.invoice_line.save()
diff --git a/modules/project_invoice/tests/scenario_project_invoice_progress.rst b/modules/project_invoice/tests/scenario_project_invoice_progress.rst
index f4182b9a56..019877a1d3 100644
--- a/modules/project_invoice/tests/scenario_project_invoice_progress.rst
+++ b/modules/project_invoice/tests/scenario_project_invoice_progress.rst
@@ -194,3 +194,17 @@ Invoice again project::
     Decimal('0.00')
     >>> project.invoiced_amount
     Decimal('136.00')
+
+Try to change invoice line quantity::
+
+    >>> set_user(1)
+    >>> ProjectWork = Model.get('project.work')
+    >>> task = ProjectWork(task.id)
+    >>> invoice_line = task.invoiced_progress[0].invoice_line
+    >>> invoice_line.quantity = 2.
+    >>> invoice_line.save()  # doctest: +IGNORE_EXCEPTION_DETAIL
+    Traceback (most recent call last):
+        ...
+    InvoiceLineValidationError: ...
+    >>> invoice_line.quantity = 2.5
+    >>> invoice_line.save()
diff --git a/modules/project_invoice/tests/scenario_project_invoice_timesheet.rst b/modules/project_invoice/tests/scenario_project_invoice_timesheet.rst
index 4dab1b1101..82557002be 100644
--- a/modules/project_invoice/tests/scenario_project_invoice_timesheet.rst
+++ b/modules/project_invoice/tests/scenario_project_invoice_timesheet.rst
@@ -225,3 +225,16 @@ Invoice again project::
     >>> _, _, invoice = Invoice.find([], order=[('id', 'ASC')])
     >>> invoice.total_amount
     Decimal('80.00')
+
+Try to change invoice line quantity::
+
+    >>> set_user(1)
+    >>> TimesheetLine = Model.get('timesheet.line')
+    >>> line = TimesheetLine(line.id)
+    >>> line.invoice_line.quantity = 5
+    >>> line.invoice_line.save()  # doctest: +IGNORE_EXCEPTION_DETAIL
+    Traceback (most recent call last):
+        ...
+    InvoiceLineValidationError: ...
+    >>> line.invoice_line.quantity = 4
+    >>> line.invoice_line.save()