diff --git a/app/errors.py b/app/errors.py
index 67448e1fb..09ff8d633 100644
--- a/app/errors.py
+++ b/app/errors.py
@@ -111,5 +111,8 @@ def register_errors(blueprint):
     @blueprint.app_errorhandler(500)
     @blueprint.errorhandler(Exception)
     def internal_server_error(e):
+        # if e is a werkzeug InternalServerError then it may wrap the original exception. For more details see:
+        # https://flask.palletsprojects.com/en/1.1.x/errorhandling/?highlight=internalservererror#unhandled-exceptions
+        e = getattr(e, 'original_exception', e)
         current_app.logger.exception(e)
         return jsonify(result='error', message="Internal server error"), 500
diff --git a/requirements-app.txt b/requirements-app.txt
index b72629c26..f628c38e6 100644
--- a/requirements-app.txt
+++ b/requirements-app.txt
@@ -15,7 +15,7 @@ gunicorn==19.7.1  # pyup: ignore, >19.8 breaks eventlet patching
 iso8601==0.1.12
 jsonschema==3.0.2
 marshmallow-sqlalchemy==0.17.0
-marshmallow==3.0.1
+marshmallow==2.20.2  # pyup: <3 throws errors
 psycopg2-binary==2.8.3
 PyJWT==1.7.1
 SQLAlchemy==1.3.8
diff --git a/requirements.txt b/requirements.txt
index 62c4af0b6..b74c9de73 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -17,7 +17,7 @@ gunicorn==19.7.1  # pyup: ignore, >19.8 breaks eventlet patching
 iso8601==0.1.12
 jsonschema==3.0.2
 marshmallow-sqlalchemy==0.17.0
-marshmallow==3.0.1
+marshmallow==2.20.2  # pyup: <3 throws errors
 psycopg2-binary==2.8.3
 PyJWT==1.7.1
 SQLAlchemy==1.3.8