diff --git a/Tools/environment_install/install-prereqs-ubuntu.sh b/Tools/environment_install/install-prereqs-ubuntu.sh
index 82b7ae8c27..e5040e771f 100755
--- a/Tools/environment_install/install-prereqs-ubuntu.sh
+++ b/Tools/environment_install/install-prereqs-ubuntu.sh
@@ -147,11 +147,12 @@ fi
 
 # Lists of packages to install
 BASE_PKGS="build-essential ccache g++ gawk git make wget valgrind screen"
+PYTHON_PKGS="future lxml pymavlink pyserial MAVProxy pexpect geocoder empy ptyprocess dronecan"
 if [ ${RELEASE_CODENAME} == 'bionic' ]; then
     # use fixed version for package that drop python2 support
-    PYTHON_PKGS="future lxml pymavlink MAVProxy pexpect flake8==3.7.9 requests==2.27.1 monotonic==1.6 geocoder empy ptyprocess configparser==4.0.2 click==7.1.2 decorator==4.4.2 dronecan"
+    PYTHON_PKGS="$PYTHON_PKGS flake8==3.7.9 requests==2.27.1 monotonic==1.6 configparser==4.0.2 click==7.1.2 decorator==4.4.2"
 else
-    PYTHON_PKGS="future lxml pymavlink MAVProxy pexpect flake8 geocoder empy ptyprocess dronecan"
+    PYTHON_PKGS="$PYTHON_PKGS flake8"
 fi
 
 # add some Python packages required for commonly-used MAVProxy modules and hex file generation:
@@ -176,7 +177,7 @@ fi
 # add some packages required for commonly-used MAVProxy modules:
 if [[ $SKIP_AP_GRAPHIC_ENV -ne 1 ]]; then
   if [ ${RELEASE_CODENAME} == 'lunar' ]; then
-        PYTHON_PKGS+=" matplotlib serial scipy opencv-python pyyaml"
+        PYTHON_PKGS+=" matplotlib scipy opencv-python pyyaml"
         SITL_PKGS+=" xterm libcsfml-dev libcsfml-audio${SITLCFML_VERSION} libcsfml-dev libcsfml-graphics${SITLCFML_VERSION} libcsfml-network${SITLCFML_VERSION} libcsfml-system${SITLCFML_VERSION} libcsfml-window${SITLCFML_VERSION} libsfml-audio${SITLFML_VERSION} libsfml-dev libsfml-graphics${SITLFML_VERSION} libsfml-network${SITLFML_VERSION} libsfml-system${SITLFML_VERSION} libsfml-window${SITLFML_VERSION}"
   else
   SITL_PKGS="$SITL_PKGS xterm ${PYTHON_V}-matplotlib ${PYTHON_V}-serial ${PYTHON_V}-scipy ${PYTHON_V}-opencv libcsfml-dev libcsfml-audio${SITLCFML_VERSION} libcsfml-dev libcsfml-graphics${SITLCFML_VERSION} libcsfml-network${SITLCFML_VERSION} libcsfml-system${SITLCFML_VERSION} libcsfml-window${SITLCFML_VERSION} libsfml-audio${SITLFML_VERSION} libsfml-dev libsfml-graphics${SITLFML_VERSION} libsfml-network${SITLFML_VERSION} libsfml-system${SITLFML_VERSION} libsfml-window${SITLFML_VERSION} ${PYTHON_V}-yaml"