diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a493401d98bdea0e629d01ad25965392607ba302..aa60a1b1fc7004324d05274788d79bf77321ef40 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -11,8 +11,8 @@ variables:
   stage: test
   before_script:
     - apt-get update && apt-get install -y --allow-unauthenticated libsasl2-dev libssl-dev locales locales-all
-    - pip install -r requirements.txt --default-timeout=180 -i https://pypi.lcsb.uni.lu/simple/
-    - pip install -r requirements-dev.txt --default-timeout=180 -i https://pypi.lcsb.uni.lu/simple/
+    - pip install --use-deprecated=legacy-resolver -r requirements.txt --default-timeout=180 -i https://pypi.lcsb.uni.lu/simple/
+    - pip install --use-deprecated=legacy-resolver -r requirements-dev.txt --default-timeout=180 -i https://pypi.lcsb.uni.lu/simple/
 
 test_postgres:
     <<: *test_definition
diff --git a/Dockerfile b/Dockerfile
index 0b52e1a3990087a573d328adcf7ee6df58872505..955f7115fc7acd0bcd0287a0e5c64c56fb3ea543 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,7 +4,7 @@ RUN mkdir /code
 WORKDIR /code
 RUN apt-get update && apt-get install -y --allow-unauthenticated libsasl2-dev libssl-dev locales locales-all 
 ADD requirements* /code/
-RUN pip install -r requirements.txt --default-timeout=180 -i https://pypi.lcsb.uni.lu/simple/ && pip install -r requirements-dev.txt --default-timeout=180 -i https://pypi.lcsb.uni.lu/simple/ # --use-feature=2020-resolver
+RUN pip install --use-deprecated=legacy-resolver -r requirements.txt --default-timeout=180 -i https://pypi.lcsb.uni.lu/simple/ && pip install --use-deprecated=legacy-resolver -r requirements-dev.txt --default-timeout=180 -i https://pypi.lcsb.uni.lu/simple/ # --use-feature=2020-resolver
 ADD . /code/
 RUN cp local_settings_ci.py smash/smash/local_settings.py
 WORKDIR /code/smash
diff --git a/debian-template/postinst b/debian-template/postinst
index c6f237ddcdbee5217f65bbb0896239ba1ae2bcfe..3994404ade00b3db778141e69a1f5b5ff4190e88 100644
--- a/debian-template/postinst
+++ b/debian-template/postinst
@@ -26,8 +26,8 @@ fi
 
 echo "Installing python dependencies"
 {
-  source /usr/lib/smasch/env/bin/activate && pip install -r /usr/lib/smasch/requirements.txt --log $LOG_FILE
-  source /usr/lib/smasch/env/bin/activate && pip install -r /usr/lib/smasch/requirements-dev.txt  --log $LOG_FILE
+  source /usr/lib/smasch/env/bin/activate && pip install -r --use-deprecated=legacy-resolver /usr/lib/smasch/requirements.txt --log $LOG_FILE
+  source /usr/lib/smasch/env/bin/activate && pip install -r --use-deprecated=legacy-resolver /usr/lib/smasch/requirements-dev.txt  --log $LOG_FILE
 } || {
   echo "There was an issue when installing python dependencies." >> $LOG_FILE
   echo "There was an issue when installing python dependencies. Reinstall of smasch could help (in case you are upgrading smasch the data should not be lost in the process): "
diff --git a/readme.md b/readme.md
index 384c620547a0e48da3624d9f09e37f2203288687..d845098c1c8788ac627700f933cbeb5cfb87219b 100644
--- a/readme.md
+++ b/readme.md
@@ -26,7 +26,7 @@ python manage.py createsuperuser
   - `cd scheduling-system`
   - `virtualenv env` to create new virtualenv (contains clean python working environment)
   - `. env/bin/activate` (to start using virtualenv)
-  - `pip install -r requirements.txt` to install project's dependencies
+  - `pip install --use-deprecated=legacy-resolver -r requirements.txt` to install project's dependencies
   - Create `local_settings.py` file in `(./scheduling-system)/smash/smash` directory by copying the template in `(./scheduling-system)/smash/smash/local_settings.template` and edit your local_setttings.py file to change your database connection data.
 
  - Update migration db scrpit from file structure (`./scheduling-system/smash/manage.py makemigrations`)