diff --git a/src/filesystem/implementation.js b/src/filesystem/implementation.js
index 6f15e2c..6f69631 100644
--- a/src/filesystem/implementation.js
+++ b/src/filesystem/implementation.js
@@ -1875,7 +1875,7 @@ function appendFile(fs, context, path, data, options, callback) {
   if(typeof data === 'number') {
     data = '' + data;
   }
-  if(typeof data === 'string' && options.encoding === 'utf8') {
+  if(typeof data === 'string' && (options.encoding == null || options.encoding === 'utf8')) {
     data = Encoding.encode(data);
   }
 
diff --git a/tests/spec/fs.appendFile.spec.js b/tests/spec/fs.appendFile.spec.js
index 7fb3aa9..b57777a 100644
--- a/tests/spec/fs.appendFile.spec.js
+++ b/tests/spec/fs.appendFile.spec.js
@@ -65,6 +65,38 @@ describe('fs.appendFile', function() {
       });
     });
   });
+    
+  it('should append without error when explcitly entering encoding and flag options (default values)' , function(done) {
+    var fs = util.fs();
+    var contents = 'This is a file.';
+    var more = ' Appended.';
+
+    fs.appendFile('/myfile', more , {encoding: 'utf8', flag: 'a'}, function(error) {
+      if(error) throw error;
+
+      fs.readFile('/myfile', { encoding: 'utf8' }, function(error, data) {
+        expect(error).not.to.exist;
+        expect(data).to.equal(contents + more);
+        done();
+      });
+    });
+  });
+
+  it('should append without error when specfifying flag option (default value)' , function(done) {
+    var fs = util.fs();
+    var contents = 'This is a file.';
+    var more = ' Appended.';
+
+    fs.appendFile('/myfile', more , {flag: 'a'}, function(error) {
+      if(error) throw error;
+
+      fs.readFile('/myfile', { encoding: 'utf8' }, function(error, data) {
+        expect(error).not.to.exist;
+        expect(data).to.equal(contents + more);
+        done();
+      });
+    });
+  });
 
   it('should append a binary file', function(done) {
     var fs = util.fs();