diff --git a/lib/mapnik.js b/lib/mapnik.js
index <HASH>..<HASH> 100644
--- a/lib/mapnik.js
+++ b/lib/mapnik.js
@@ -11,9 +11,11 @@ var sm = new (require('sphericalmercator'));
 
 var cache = {};
 
-// Increase number of threads to 1.5x the number of logical CPUs.
-var threads = Math.ceil(Math.max(4, require('os').cpus().length * 1.5));
-require('eio').setMinParallel(threads);
+if (process.platform !== 'win32') {
+    // Increase number of threads to 1.5x the number of logical CPUs.
+    var threads = Math.ceil(Math.max(4, require('os').cpus().length * 1.5));
+    require('eio').setMinParallel(threads);
+}
 
 exports = module.exports = MapnikSource;
node-eio only makes sense on unix