diff --git a/cal_tools/cal_tools/tools.py b/cal_tools/cal_tools/tools.py
index 34f8e211dcf6340e9b94a9fbb07508840d5ec234..d5477e9f6037d2005d66aa5b9a5cba02628bd67a 100644
--- a/cal_tools/cal_tools/tools.py
+++ b/cal_tools/cal_tools/tools.py
@@ -415,6 +415,9 @@ def get_constant_from_db_and_time(device, constant, condition, empty_constant,
         if m.comm_db_success:
             return data, m.calibration_constant_version.begin_at
         else:
+            # retun none for injection time if communication with db failed.
+            # reasons (no constant or condition found,
+            # or network problem)
             return data, None
     else:
         return data, None
diff --git a/notebooks/AGIPD/AGIPD_Correct_and_Verify.ipynb b/notebooks/AGIPD/AGIPD_Correct_and_Verify.ipynb
index 3d34b7934b7a7b73899a8fe4ed869dbbdfbfbdf3..2bb9fdeae0b184a8ea8bd260cd0f4a32ad11316d 100644
--- a/notebooks/AGIPD/AGIPD_Correct_and_Verify.ipynb
+++ b/notebooks/AGIPD/AGIPD_Correct_and_Verify.ipynb
@@ -641,9 +641,6 @@
     "        for key, item in when.items():\n",
     "            if hasattr(item, 'strftime'):\n",
     "                item = item.strftime('%y-%m-%d %H:%M')\n",
-    "            # If constant retrieval is crashed\n",
-    "            else:\n",
-    "                item = 'None'\n",
     "            when[key] = item\n",
     "            print('{:.<12s}'.format(key), item)\n",
     "            \n",