diff --git a/lib/less/index.js b/lib/less/index.js
index 5f990f15..84086ec2 100644
--- a/lib/less/index.js
+++ b/lib/less/index.js
@@ -38,11 +38,17 @@ var less = {
         var extract = ctx.extract;
         var error = [];
 
-        extract[0] && error.push(stylize((ctx.line - 1) + ' ' + extract[0], 'grey'));
+        if (typeof(extract[0]) === 'string') {
+            error.push(stylize((ctx.line - 1) + ' ' + extract[0], 'grey'));
+        }
+
         error.push(ctx.line + ' ' + stylize(extract[1].slice(0, ctx.column), 'green')
                             + stylize(stylize(extract[1][ctx.column], 'inverse')
                             + extract[1].slice(ctx.column + 1), 'yellow'));
-        extract[2] && error.push(stylize((ctx.line + 1) + ' ' + extract[2], 'grey'));
+
+        if (typeof(extract[2]) === 'string') {
+            error.push(stylize((ctx.line + 1) + ' ' + extract[2], 'grey'));
+        }
         error = error.join('\n') + '\033[0m\n';
 
         require('sys').puts(stylize(ctx.message, 'red'), error);