diff --git a/start-app.sh b/start-app.sh
index 156743f4..46c8873c 100755
--- a/start-app.sh
+++ b/start-app.sh
@@ -1,13 +1,28 @@
 #!/bin/bash -e
 
-venvdir=~/.virtualenvs/$(basename $(cd $(dirname $0) && pwd -P))-$1-$2
+VENV_DIR=~/.virtualenvs/$(basename $(cd $(dirname $0) && pwd -P))-$1-$2
+LOCK_DIR=./tmp-start
 
-if [ ! -d "${venvdir}" ]; then
-    virtualenv --no-site-packages "$venvdir"
+trap "rm -rf $LOCK_DIR" EXIT INT TERM
+
+waiting=0
+until mkdir $LOCK_DIR > /dev/null 2>&1; do
+    if [ $waiting -eq 0 ]; then
+        echo "waiting for startup lock"
+        waiting=1
+    fi
+    sleep 1
+done
+
+if [ ! -d "${VENV_DIR}" ]; then
+    virtualenv --no-site-packages "$VENV_DIR"
 fi
 
-source "$venvdir/bin/activate"
+source "$VENV_DIR/bin/activate"
 
+echo "Installing dependencies"
 pip install -r requirements.txt
 
+rmdir $LOCK_DIR
+
 python start.py $1 $2