diff --git a/greenmine/projects/issues/serializers.py b/greenmine/projects/issues/serializers.py
index d8e35957..1a6b2b50 100644
--- a/greenmine/projects/issues/serializers.py
+++ b/greenmine/projects/issues/serializers.py
@@ -70,11 +70,12 @@ class IssueSerializer(serializers.ModelSerializer):
         diff_list = []
         current = None
 
-        for version in reversed(list(reversion.get_for_object(obj))):
-            if current:
-                issues_diff = self.get_issues_diff(current, version)
-                diff_list.append(issues_diff)
+        if obj:
+            for version in reversed(list(reversion.get_for_object(obj))):
+                if current:
+                    issues_diff = self.get_issues_diff(current, version)
+                    diff_list.append(issues_diff)
 
-            current = version
+                current = version
 
         return diff_list
diff --git a/greenmine/projects/tasks/serializers.py b/greenmine/projects/tasks/serializers.py
index ab9f02b2..5803f921 100644
--- a/greenmine/projects/tasks/serializers.py
+++ b/greenmine/projects/tasks/serializers.py
@@ -53,11 +53,12 @@ class TaskSerializer(serializers.ModelSerializer):
         diff_list = []
         current = None
 
-        for version in reversed(list(reversion.get_for_object(obj))):
-            if current:
-                task_diff = self.get_task_diff(current, version)
-                diff_list.append(task_diff)
+        if obj:
+            for version in reversed(list(reversion.get_for_object(obj))):
+                if current:
+                    task_diff = self.get_task_diff(current, version)
+                    diff_list.append(task_diff)
 
-            current = version
+                current = version
 
         return diff_list
diff --git a/greenmine/projects/userstories/serializers.py b/greenmine/projects/userstories/serializers.py
index 553bff22..70213296 100644
--- a/greenmine/projects/userstories/serializers.py
+++ b/greenmine/projects/userstories/serializers.py
@@ -84,11 +84,12 @@ class UserStorySerializer(serializers.ModelSerializer):
         diff_list = []
         current = None
 
-        for version in reversed(list(reversion.get_for_object(obj))):
-            if current:
-                us_diff = self.get_user_stories_diff(current, version)
-                diff_list.append(us_diff)
+        if obj:
+            for version in reversed(list(reversion.get_for_object(obj))):
+                if current:
+                    us_diff = self.get_user_stories_diff(current, version)
+                    diff_list.append(us_diff)
 
-            current = version
+                current = version
 
         return diff_list