diff --git a/lib/database.js b/lib/database.js
index 91eb0b3..77aa2d6 100644
--- a/lib/database.js
+++ b/lib/database.js
@@ -177,7 +177,7 @@ function get_market_data(market, cb) {
 function create_lock(lockfile, cb) {
   if (settings.lock_during_index == true) {
     var fname = './tmp/' + lockfile + '.pid';
-    fs.appendFile(fname, process.pid, function (err) {
+    fs.appendFile(fname, process.pid.toString(), function (err) {
       if (err) {
         console.log("Error: unable to create %s", fname);
         process.exit(1);
diff --git a/scripts/sync.js b/scripts/sync.js
index 486891a..a302fc8 100644
--- a/scripts/sync.js
+++ b/scripts/sync.js
@@ -68,7 +68,7 @@ if (process.argv[2] == 'index') {
 function create_lock(cb) {
   if ( database == 'index' ) {
     var fname = './tmp/' + database + '.pid';
-    fs.appendFile(fname, process.pid, function (err) {
+    fs.appendFile(fname, process.pid.toString(), function (err) {
       if (err) {
         console.log("Error: unable to create %s", fname);
         process.exit(1);