diff --git a/bwakit/bwa-postalt.js b/bwakit/bwa-postalt.js
index bfc41900..e00d3dc7 100644
--- a/bwakit/bwa-postalt.js
+++ b/bwakit/bwa-postalt.js
@@ -283,7 +283,7 @@ function bwa_postalt(args)
 	// process SAM
 	var buf2 = [], hla = {};
 	file = args.length - getopt.ind >= 2? new File(args[getopt.ind+1]) : new File();
-	while (file.readline(buf) >= 0) {
+	while (file.readline(buf) > 0) {
 		var m, line = buf.toString();
 
 		if (line.charAt(0) == '@') { // print and then skip the header line