diff --git a/deepomatic/api/http_helper.py b/deepomatic/api/http_helper.py
index 710f20a..48f31bf 100644
--- a/deepomatic/api/http_helper.py
+++ b/deepomatic/api/http_helper.py
@@ -209,15 +209,41 @@ def recursive_json_dump(prefix, obj, data_dict, omit_dot=False):
         return new_dict
 
     def send_request(self, requests_callable, *args, **kwargs):
-        # requests_callable must be a method from the requests module
-
         # this is the timeout of requests module
         requests_timeout = kwargs.pop('timeout', self.requests_timeout)
+
+        files = kwargs.pop('files', None)
+        if files:
+            for key, f in files.items():
+                # file can be a tuple
+                # if so, the fileobj is in second position
+                if isinstance(f, (tuple, list)):
+                    f = f[1]
+                if f is None or isinstance(f, (string_types, bytes, bytearray, int, float, bool)):
+                    continue
+                error = "Unsupported file object type '{}' for key '{}'".format(type(f), key)
+                # seek files before each retry, to avoid silently retrying with different input
+                if hasattr(f, 'seek'):
+                    if hasattr(f, 'seekable') and not f.seekable():
+                        raise DeepomaticException("{}: not seekable".format(error))
+                    f.seek(0)
+                    continue
+
+                raise DeepomaticException("{}: not a scalar or seekable.".format(error))
+
+        return requests_callable(*args, files=files,
+                                 timeout=requests_timeout,
+                                 verify=self.verify_ssl,
+                                 **kwargs)
+
+    def maybe_retry_send_request(self, requests_callable, *args, **kwargs):
+        # requests_callable must be a method from the requests module
+
         http_retry = kwargs.pop('http_retry', self.http_retry)
 
-        functor = functools.partial(requests_callable, *args,
-                                    verify=self.verify_ssl,
-                                    timeout=requests_timeout, **kwargs)
+        functor = functools.partial(self.send_request,
+                                    requests_callable,
+                                    *args, **kwargs)
 
         if http_retry is not None:
             return http_retry.retry(functor)
@@ -274,10 +300,10 @@ def make_request(self, func, resource, params=None, data=None,
         if not resource.startswith('http'):
             resource = self.resource_prefix + resource
 
-        response = self.send_request(func, resource, *args,
-                                     params=params, data=data,
-                                     files=files, headers=headers,
-                                     stream=stream, **kwargs)
+        response = self.maybe_retry_send_request(func, resource, *args,
+                                                 params=params, data=data,
+                                                 files=files, headers=headers,
+                                                 stream=stream, **kwargs)
 
         # Close opened files
         for file in opened_files:
diff --git a/deepomatic/api/version.py b/deepomatic/api/version.py
index f4f3cf1..a7fa864 100644
--- a/deepomatic/api/version.py
+++ b/deepomatic/api/version.py
@@ -1,6 +1,6 @@
 __title__ = 'deepomatic-api'
 __description__ = 'Deepomatic API client'
-__version__ = '0.9.2'
+__version__ = '0.9.3'
 __author__ = 'deepomatic'
 __author_email__ = 'support@deepomatic.com'
 __url__ = 'https://github.com/deepomatic/deepomatic-client-python'
diff --git a/demo.py b/demo.py
index 6847e0f..1f7013a 100644
--- a/demo.py
+++ b/demo.py
@@ -359,7 +359,7 @@ def download_file(url):
     filename = os.path.join(tempfile.gettempdir(),
                             hashlib.sha1(url.encode()).hexdigest() + ext)
     if os.path.exists(filename):  # avoid redownloading
-        logger.info("Skipping download of {}: file already exist in ".format(url, filename))
+        logger.info("Skipping download of {}: file already exist in {}".format(url, filename))
         return filename
     r = requests.get(url, stream=True)
     r.raise_for_status()
diff --git a/requirements.dev.txt b/requirements.dev.txt
index 6a2542d..a579324 100644
--- a/requirements.dev.txt
+++ b/requirements.dev.txt
@@ -3,3 +3,4 @@ pytest==4.6.5
 pytest-cov==2.7.1
 pytest-voluptuous==1.1.0
 httpretty==0.9.6
+flake8==3.8.4
diff --git a/requirements.txt b/requirements.txt
index 01fca15..9e16833 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,4 +3,3 @@ promise>=2.1,<3
 six>=1.10.0,<2
 requests>=2.19.0,<3  # will not work below in python3
 tenacity>=5.1,<6
-flake8>=3.7,<4
diff --git a/setup.py b/setup.py
index 58addf5..f0d6af7 100644
--- a/setup.py
+++ b/setup.py
@@ -2,17 +2,9 @@
 import io
 from setuptools import find_packages, setup
 
-try:
-    # for pip >= 10
-    from pip._internal.req import parse_requirements
-except ImportError:
-    # for pip <= 9.0.3
-    from pip.req import parse_requirements
-
 
 here = os.path.abspath(os.path.dirname(__file__))
 
-
 about = {}
 with io.open(os.path.join(here, 'deepomatic', 'api', 'version.py'), 'r', encoding='utf-8') as f:
     exec(f.read(), about)
@@ -24,7 +16,8 @@
 os.chdir(os.path.normpath(os.path.join(os.path.abspath(__file__), os.pardir)))
 
 # Read requirements
-install_reqs = parse_requirements(os.path.join(here, 'requirements.txt'), session='hack')
+with io.open(os.path.join(here, 'requirements.txt'), encoding='utf-8') as f:
+    requirements = f.readlines()
 
 namespaces = ['deepomatic']
 
@@ -43,7 +36,7 @@
     long_description=README,
     long_description_content_type='text/markdown',
     data_files=[('', ['requirements.txt'])],
-    install_requires=[str(ir.req) for ir in install_reqs],
+    install_requires=requirements,
     python_requires=">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*",
     classifiers=[
         'Operating System :: OS Independent',