diff --git a/moto/ec2/models.py b/moto/ec2/models.py
index db2b71bcb..9707eb973 100644
--- a/moto/ec2/models.py
+++ b/moto/ec2/models.py
@@ -774,9 +774,9 @@ class TagBackend(object):
             raise InvalidParameterValueErrorTagNull()
         for resource_id in resource_ids:
             if resource_id in self.tags:
-                if len(self.tags[resource_id]) + len(tags) > 10:
+                if len(self.tags[resource_id]) + len([tag for tag in tags if not tag.startswith("aws:")]) > 10:
                     raise TagLimitExceeded()
-            elif len(tags) > 10:
+            elif len([tag for tag in tags if not tag.startswith("aws:")]) > 10:
                 raise TagLimitExceeded()
         for resource_id in resource_ids:
             for tag in tags: