diff --git a/odoo/addons/base/models/assetsbundle.py b/odoo/addons/base/models/assetsbundle.py
index a6487c38a51..b06aa2a4a90 100644
--- a/odoo/addons/base/models/assetsbundle.py
+++ b/odoo/addons/base/models/assetsbundle.py
@@ -193,14 +193,18 @@ class AssetsBundle(object):
         return response
 
     @func.lazy_property
-    def last_modified(self):
+    def last_modified_combined(self):
         """Returns last modified date of linked files"""
+        # WebAsset are recreate here when a better solution would be to use self.stylesheets and self.javascripts
+        # We currently have no garanty that they are present since it will depends on js and css parameters
+        # last_modified is actually only usefull for the checksum and checksum should be extension specific since
+        # they are differents bundles. This will be a future work.
+
+        # changing the logic from max date to combined date to fix bundle invalidation issues.
         assets = [WebAsset(self, url=f['url'], filename=f['filename'], inline=f['content'])
             for f in self.files
             if f['atype'] in ['text/sass', "text/scss", "text/less", "text/css", "text/javascript", "text/xml"]]
-        return max(itertools.chain(
-            (asset.last_modified for asset in assets),
-        ))
+        return ','.join(str(asset.last_modified) for asset in assets)
 
     @func.lazy_property
     def version(self):
@@ -210,9 +214,9 @@ class AssetsBundle(object):
     def checksum(self):
         """
         Not really a full checksum.
-        We compute a SHA512/256 on the rendered bundle + max linked files last_modified date
+        We compute a SHA512/256 on the rendered bundle + combined linked files last_modified date
         """
-        check = u"%s%s" % (json.dumps(self.files, sort_keys=True), self.last_modified)
+        check = u"%s%s" % (json.dumps(self.files, sort_keys=True), self.last_modified_combined)
         return hashlib.sha512(check.encode('utf-8')).hexdigest()[:64]
 
     def _get_asset_template_url(self):
diff --git a/odoo/addons/test_assetsbundle/tests/test_assetsbundle.py b/odoo/addons/test_assetsbundle/tests/test_assetsbundle.py
index 9a5df4e8b6f..cb7bacabbff 100644
--- a/odoo/addons/test_assetsbundle/tests/test_assetsbundle.py
+++ b/odoo/addons/test_assetsbundle/tests/test_assetsbundle.py
@@ -204,7 +204,7 @@ class TestJavascriptAssetsBundle(FileTouchable):
         """
         bundle0 = self._get_asset(self.jsbundle_name)
         bundle0.js()
-        last_modified0 = bundle0.last_modified
+        last_modified0 = bundle0.last_modified_combined
         version0 = bundle0.version
 
         path = get_resource_path('test_assetsbundle', 'static', 'src', 'js', 'test_jsfile1.js')
@@ -212,7 +212,7 @@ class TestJavascriptAssetsBundle(FileTouchable):
 
         with self._touch(path):
             bundle1.js()
-            last_modified1 = bundle1.last_modified
+            last_modified1 = bundle1.last_modified_combined
             version1 = bundle1.version
             self.assertNotEqual(last_modified0, last_modified1,
                                 "the creation date of the ir.attachment should change because the bundle has changed.")
@@ -486,13 +486,13 @@ class TestJavascriptAssetsBundle(FileTouchable):
         # Assets access for en_US language
         ltr_bundle0 = self._get_asset(self.cssbundle_name)
         ltr_bundle0.css()
-        ltr_last_modified0 = ltr_bundle0.last_modified
+        ltr_last_modified0 = ltr_bundle0.last_modified_combined
         ltr_version0 = ltr_bundle0.version
 
         # Assets access for ar_SY language
         rtl_bundle0 = self._get_asset(self.cssbundle_name, env=self.env(context={'lang': 'ar_SY'}))
         rtl_bundle0.css()
-        rtl_last_modified0 = rtl_bundle0.last_modified
+        rtl_last_modified0 = rtl_bundle0.last_modified_combined
         rtl_version0 = rtl_bundle0.version
 
         # Touch test_cssfile1.css
@@ -502,7 +502,7 @@ class TestJavascriptAssetsBundle(FileTouchable):
 
         with self._touch(path):
             ltr_bundle1.css()
-            ltr_last_modified1 = ltr_bundle1.last_modified
+            ltr_last_modified1 = ltr_bundle1.last_modified_combined
             ltr_version1 = ltr_bundle1.version
             ltr_ira1 = self._any_ira_for_bundle('min.css')
             self.assertNotEqual(ltr_last_modified0, ltr_last_modified1)
@@ -511,7 +511,7 @@ class TestJavascriptAssetsBundle(FileTouchable):
             rtl_bundle1 = self._get_asset(self.cssbundle_name, env=self.env(context={'lang': 'ar_SY'}))
 
             rtl_bundle1.css()
-            rtl_last_modified1 = rtl_bundle1.last_modified
+            rtl_last_modified1 = rtl_bundle1.last_modified_combined
             rtl_version1 = rtl_bundle1.version
             rtl_ira1 = self._any_ira_for_bundle('min.css', lang='ar_SY')
             self.assertNotEqual(rtl_last_modified0, rtl_last_modified1)