diff --git a/taiga/projects/history/models.py b/taiga/projects/history/models.py
index 82d1667d..ae0dd356 100644
--- a/taiga/projects/history/models.py
+++ b/taiga/projects/history/models.py
@@ -94,7 +94,10 @@ class HistoryEntry(models.Model):
     def owner(self):
         pk = self.user["pk"]
         model = apps.get_model("users", "User")
-        return model.objects.get(pk=pk)
+        try:
+            return model.objects.get(pk=pk)
+        except model.DoesNotExist:
+            return None
 
     @cached_property
     def values_diff(self):
diff --git a/taiga/projects/history/serializers.py b/taiga/projects/history/serializers.py
index 2b5f4e00..ac6cf0d2 100644
--- a/taiga/projects/history/serializers.py
+++ b/taiga/projects/history/serializers.py
@@ -39,12 +39,13 @@ class HistoryEntrySerializer(serializers.ModelSerializer):
     def get_user(self, entry):
         user = {"pk": None, "username": None, "name": None, "photo": None, "is_active": False}
         user.update(entry.user)
-
         user["photo"] = get_photo_or_gravatar_url(entry.owner)
-        user["is_active"] = entry.owner.is_active
 
-        if entry.owner.is_active or entry.owner.is_system:
-            user["name"] = entry.owner.get_full_name()
-            user["username"] = entry.owner.username
+        if entry.owner:
+            user["is_active"] = entry.owner.is_active
+
+            if entry.owner.is_active or entry.owner.is_system:
+                user["name"] = entry.owner.get_full_name()
+                user["username"] = entry.owner.username
 
         return user
diff --git a/taiga/users/services.py b/taiga/users/services.py
index 0ce318bd..4be2f405 100644
--- a/taiga/users/services.py
+++ b/taiga/users/services.py
@@ -34,6 +34,7 @@ from taiga.projects.notifications.choices import NotifyLevel
 
 from .gravatar import get_gravatar_url
 
+from django.conf import settings
 
 def get_and_validate_user(*, username:str, password:str) -> bool:
     """
@@ -70,7 +71,7 @@ def get_photo_or_gravatar_url(user):
     """Get the user's photo/gravatar url."""
     if user:
         return get_photo_url(user.photo) if user.photo else get_gravatar_url(user.email)
-    return ""
+    return settings.GRAVATAR_DEFAULT_AVATAR
 
 
 def get_big_photo_url(photo):