diff --git a/backup.sh b/backup.sh
index 18d2cc0..4479f0f 100755
--- a/backup.sh
+++ b/backup.sh
@@ -159,7 +159,7 @@ rcon-command () {
     RESPONSE=$(read-response "$IN_PIPE")
 
     RESPONSE_REQUEST_ID=$(response-request-id "$RESPONSE")
-    if [ "$RESPONSE_REQUEST_ID" -eq -1 ] || [ "$RESPONSE_REQUEST_ID" -eq 4294967295 ]; then
+    if [[ "$RESPONSE_REQUEST_ID" == "-1" ]] || [[ "$RESPONSE_REQUEST_ID" == "4294967295" ]]; then
       log-warning "RCON connection failed: Wrong RCON password" 1>&2
       return 1
     fi
diff --git a/test/test.sh b/test/test.sh
index d543f08..1becca5 100755
--- a/test/test.sh
+++ b/test/test.sh
@@ -16,10 +16,14 @@ setUp () {
   echo "file3" > "$TEST_TMP/server/world/file3.txt"
 
   screen -dmS "$SCREEN_TMP" bash
-  sleep 0.1
+  while ! screen -S "$SCREEN_TMP" -Q "select" . &>/dev/null; do
+    sleep 0.1
+  done
   screen -S "$SCREEN_TMP" -X stuff "cat > $TEST_TMP/screen-output\n"
   tmux new-session -d -s "$SCREEN_TMP"
-  sleep 0.1
+  while ! tmux has-session -t "$SCREEN_TMP" 2>/dev/null; do
+    sleep 0.1
+  done
   tmux send-keys -t "$SCREEN_TMP" "cat > $TEST_TMP/tmux-output" ENTER
   python test/mock_rcon.py "$RCON_PORT" "$RCON_PASSWORD" > "$TEST_TMP/rcon-output" &
   echo "$!" > "$TEST_TMP/rcon-pid"