diff --git a/lib/infra b/lib/infra
index 3d68e45bd9..eb8000e8d3 100644
--- a/lib/infra
+++ b/lib/infra
@@ -30,8 +30,6 @@ REQUIREMENTS_DIR=$DEST/requirements
 # install_infra() - Collect source and prepare
 function install_infra {
     local PIP_VIRTUAL_ENV="$REQUIREMENTS_DIR/.venv"
-    # bring down global requirements
-    git_clone $REQUIREMENTS_REPO $REQUIREMENTS_DIR $REQUIREMENTS_BRANCH
     [ ! -d $PIP_VIRTUAL_ENV ] && virtualenv $PIP_VIRTUAL_ENV
     # We don't care about testing git pbr in the requirements venv.
     PIP_VIRTUAL_ENV=$PIP_VIRTUAL_ENV pip_install -U pbr
diff --git a/stack.sh b/stack.sh
index cc8bc8c88f..2288af57a4 100755
--- a/stack.sh
+++ b/stack.sh
@@ -698,6 +698,11 @@ fi
 
 TRACK_DEPENDS=${TRACK_DEPENDS:-False}
 
+# Bring down global requirements before any use of pip_install. This is
+# necessary to ensure that the constraints file is in place before we
+# attempt to apply any constraints to pip installs.
+git_clone $REQUIREMENTS_REPO $REQUIREMENTS_DIR $REQUIREMENTS_BRANCH
+
 # Install Python packages into a virtualenv so that we can track them
 if [[ $TRACK_DEPENDS = True ]]; then
     echo_summary "Installing Python packages into a virtualenv $DEST/.venv"