diff --git a/lib/bcoin.js b/lib/bcoin.js
index 767a256a..6aa91fee 100644
--- a/lib/bcoin.js
+++ b/lib/bcoin.js
@@ -11,11 +11,8 @@ bcoin.isBrowser =
   (typeof process !== 'undefined' && process.browser)
   || typeof window !== 'undefined';
 
-if (process.env.BCOIN_DEBUG) {
-  bcoin.debug = process.env.BCOIN_DEBUG;
-  if (bcoin.debug === '0' || bcoin.debug === '1')
-    bcoin.debug = +bcoin.debug === 1;
-}
+bcoin.debug = +process.env.BCOIN_DEBUG === 1;
+bcoin.debugFile = +process.env.BCOIN_DEBUGFILE !== 0;
 
 bcoin.bn = require('bn.js');
 bcoin.elliptic = require('elliptic');
@@ -45,11 +42,6 @@ if (bcoin.fs) {
   }
 }
 
-if (bcoin.fs) {
-  bcoin._debug = bcoin.fs.createWriteStream(
-    bcoin.dir + '/debug.log', { flags: 'w' });
-}
-
 bcoin.ecdsa = bcoin.elliptic.ec('secp256k1');
 assert(!bcoin.ecdsa.signature);
 bcoin.ecdsa.signature = require('elliptic/lib/elliptic/ec/signature');
diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index 89cfe454..3631423c 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -764,9 +764,13 @@ utils.debug = function debug() {
     process.stdout.write(msg);
   }
 
-  if (bcoin._debug) {
+  if (bcoin.debugFile && bcoin.fs) {
+    if (!bcoin._debug) {
+      bcoin._debug = bcoin.fs.createWriteStream(
+        bcoin.dir + '/debug.log', { flags: 'a' });
+    }
     msg = utils.format(args, false);
-    bcoin._debug.write(msg);
+    bcoin._debug.write(process.pid + ': ' + msg);
   }
 };