diff --git a/src/filesystem/implementation.js b/src/filesystem/implementation.js
index 6f15e2c..753be93 100644
--- a/src/filesystem/implementation.js
+++ b/src/filesystem/implementation.js
@@ -1277,7 +1277,10 @@ function truncate_file(context, path, length, callback) {
     }
   }
 
-  if(length < 0) {
+  if (!Number.isInteger(length)) {
+    callback(new Errors.EINVAL('length must be a number'));
+  }
+  else if (length < 0) {
     callback(new Errors.EINVAL('length cannot be negative'));
   } else {
     find_node(context, path, read_file_data);
diff --git a/tests/spec/fs.truncate.spec.js b/tests/spec/fs.truncate.spec.js
index 4827ffe..6577752 100644
--- a/tests/spec/fs.truncate.spec.js
+++ b/tests/spec/fs.truncate.spec.js
@@ -25,6 +25,21 @@ describe('fs.truncate', function() {
     });
   });
 
+  it('should error when length is NaN', function(done) {
+    var fs = util.fs();
+    var contents = 'This is a file.';
+
+    fs.writeFile('/myfile', contents, function(error) {
+      if(error) throw error;
+
+      fs.truncate('/myfile', 'NaN', function(error) {
+        expect(error).to.exist;
+        expect(error.code).to.equal('EINVAL');
+        done();
+      });
+    });
+  });
+
   it('should error when path is not a file', function(done) {
     var fs = util.fs();