diff --git a/lib/tempest b/lib/tempest
index 8ee986d..77197c2 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -111,6 +111,21 @@
     echo $size | python3 -c "import math; print(int(math.ceil(float(int(input()) / 1024.0 ** 3))))"
 }
 
+function set_tempest_venv_constraints {
+    local tmp_c
+    tmp_c=$1
+    if [[ $TEMPEST_VENV_UPPER_CONSTRAINTS == "master" ]]; then
+        (cd $REQUIREMENTS_DIR && git show origin/master:upper-constraints.txt) > $tmp_c
+    else
+        echo "Using $TEMPEST_VENV_UPPER_CONSTRAINTS constraints in Tempest virtual env."
+        cat $TEMPEST_VENV_UPPER_CONSTRAINTS > $tmp_c
+        # NOTE: setting both tox env var and once Tempest start using new var
+        # TOX_CONSTRAINTS_FILE then we can remove the old one.
+        export UPPER_CONSTRAINTS_FILE=$TEMPEST_VENV_UPPER_CONSTRAINTS
+        export TOX_CONSTRAINTS_FILE=$TEMPEST_VENV_UPPER_CONSTRAINTS
+    fi
+}
+
 # configure_tempest() - Set config files, create data dirs, etc
 function configure_tempest {
     if [[ "$INSTALL_TEMPEST" == "True" ]]; then
@@ -617,10 +632,9 @@
         tox -revenv-tempest --notest
     fi
 
-    # The requirements might be on a different branch, while tempest needs master requirements.
     local tmp_u_c_m
     tmp_u_c_m=$(mktemp -t tempest_u_c_m.XXXXXXXXXX)
-    (cd $REQUIREMENTS_DIR && git show origin/master:upper-constraints.txt) > $tmp_u_c_m
+    set_tempest_venv_constraints $tmp_u_c_m
     tox -evenv-tempest -- pip install -c $tmp_u_c_m -r requirements.txt
     rm -f $tmp_u_c_m
 
@@ -702,6 +716,10 @@
     # TEMPEST_DIR already exist until RECLONE is true.
     git checkout $TEMPEST_BRANCH
 
+    local tmp_u_c_m
+    tmp_u_c_m=$(mktemp -t tempest_u_c_m.XXXXXXXXXX)
+    set_tempest_venv_constraints $tmp_u_c_m
+
     tox -r --notest -efull
     # TODO: remove the trailing pip constraint when a proper fix
     # arrives for bug https://bugs.launchpad.net/devstack/+bug/1906322
@@ -709,8 +727,9 @@
     # NOTE(mtreinish) Respect constraints in the tempest full venv, things that
     # are using a tox job other than full will not be respecting constraints but
     # running pip install -U on tempest requirements
-    $TEMPEST_DIR/.tox/tempest/bin/pip install -c $REQUIREMENTS_DIR/upper-constraints.txt -r requirements.txt
+    $TEMPEST_DIR/.tox/tempest/bin/pip install -c $tmp_u_c_m -r requirements.txt
     PROJECT_VENV["tempest"]=${TEMPEST_DIR}/.tox/tempest
+    rm -f $tmp_u_c_m
     popd
 }
 
@@ -718,10 +737,9 @@
 function install_tempest_plugins {
     pushd $TEMPEST_DIR
     if [[ $TEMPEST_PLUGINS != 0 ]] ; then
-        # The requirements might be on a different branch, while tempest & tempest plugins needs master requirements.
         local tmp_u_c_m
         tmp_u_c_m=$(mktemp -t tempest_u_c_m.XXXXXXXXXX)
-        (cd $REQUIREMENTS_DIR && git show origin/master:upper-constraints.txt) > $tmp_u_c_m
+        set_tempest_venv_constraints $tmp_u_c_m
         tox -evenv-tempest -- pip install -c $tmp_u_c_m $TEMPEST_PLUGINS
         rm -f $tmp_u_c_m
         echo "Checking installed Tempest plugins:"