diff --git a/lib/Image.js b/lib/Image.js
index 8319683d..980f78f8 100644
--- a/lib/Image.js
+++ b/lib/Image.js
@@ -195,7 +195,7 @@
                 throw err;
             }
         );
-    }
+    };
 
     Image.prototype.darken = function() {
         this.__lock();
@@ -494,9 +494,11 @@
                     params.interlaced = params.interlaced || defs.defaults.PNG_DEF_INTERLACED;
                     if (typeof params.interlaced !== 'boolean') throw Error('PNG \'interlaced\' must be boolean');
                     params.transparency = params.transparency || defs.defaults.PNG_DEF_TRANSPARENT;
-                    if (typeof params.transparency !== 'boolean' && params.transparency.toLowerCase() !== 'auto')
-                        throw Error('PNG \'transparency\' must be boolean or \'auto\'');
-                    if (params.transparency.toLowerCase() !== 'auto') params.transparency = that.__trans;
+                    if (typeof params.transparency !== 'boolean'){
+                        if (typeof params.transparency === 'string' && params.transparency.toLowerCase() === 'auto')
+                            params.transparency = that.__trans;
+                        else throw Error('PNG \'transparency\' must be boolean or \'auto\'');
+                    }
                     return encoder.png(
                         that.__lwip.buffer(),
                         that.__lwip.width(),
diff --git a/tests/00.argsValidation/104.image.toBuffer.js b/tests/00.argsValidation/104.image.toBuffer.js
index 9f0c1ecd..7554b632 100644
--- a/tests/00.argsValidation/104.image.toBuffer.js
+++ b/tests/00.argsValidation/104.image.toBuffer.js
@@ -7,7 +7,7 @@ var should = require("should"),
 describe('image.toBuffer arguments validation', function() {
 
     var image;
-    before(function(done) {
+    beforeEach(function(done) {
         lwip.open(imgs.jpg.rgb, function(err, img) {
             image = img;
             done(err);
@@ -34,28 +34,222 @@ describe('image.toBuffer arguments validation', function() {
 
     describe('PNG params', function() {
 
-        describe('invalid compression', function() {
-            it('should throw an error', function() {
-                image.toBuffer.bind(image, 'png', {
-                    compression: 'foo'
-                }, function() {}).should.throwError();
+        describe("valid params", function(){
+
+            describe('defaults', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', done).should.not.throwError();
+                });
             });
-        });
 
-        describe('invalid interlaced', function() {
-            it('should throw an error', function() {
-                image.toBuffer.bind(image, 'png', {
-                    interlaced: 'foo'
-                }, function() {}).should.throwError();
+            describe('none, false, true', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'none',
+                        interlaced: false,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
             });
+
+            describe('fast, false, true', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'fast',
+                        interlaced: false,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, false, true', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'high',
+                        interlaced: false,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, true, true', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'none',
+                        interlaced: true,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, true, true', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'fast',
+                        interlaced: true,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, true, true', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'high',
+                        interlaced: true,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, false, false', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'none',
+                        interlaced: false,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, false, false', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'fast',
+                        interlaced: false,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, false, false', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'high',
+                        interlaced: false,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, true, false', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'none',
+                        interlaced: true,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, true, false', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'fast',
+                        interlaced: true,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, true, false', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'high',
+                        interlaced: true,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, false, auto', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'none',
+                        interlaced: false,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, false, auto', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'fast',
+                        interlaced: false,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, false, auto', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'high',
+                        interlaced: false,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, true, auto', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'none',
+                        interlaced: true,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, true, auto', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'fast',
+                        interlaced: true,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, true, auto', function() {
+                it('should succeed', function(done) {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'high',
+                        interlaced: true,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
         });
 
-        describe('invalid transparency', function() {
-            it('should throw an error', function() {
-                image.toBuffer.bind(image, 'png', {
-                    transparency: 'foo'
-                }, function() {}).should.throwError();
+        describe("invalid params", function(){
+
+            describe('invalid compression', function() {
+                it('should throw an error', function() {
+                    image.toBuffer.bind(image, 'png', {
+                        compression: 'foo'
+                    }, function() {}).should.throwError();
+                });
+            });
+
+            describe('invalid interlaced', function() {
+                it('should throw an error', function() {
+                    image.toBuffer.bind(image, 'png', {
+                        interlaced: 'foo'
+                    }, function() {}).should.throwError();
+                });
             });
+
+            describe('invalid transparency', function() {
+                it('should throw an error', function() {
+                    image.toBuffer.bind(image, 'png', {
+                        transparency: 'foo'
+                    }, function() {}).should.throwError();
+                });
+            });
+
         });
 
     });
diff --git a/tests/00.argsValidation/204.batch.toBuffer.js b/tests/00.argsValidation/204.batch.toBuffer.js
index 55005479..9359f4dc 100644
--- a/tests/00.argsValidation/204.batch.toBuffer.js
+++ b/tests/00.argsValidation/204.batch.toBuffer.js
@@ -7,7 +7,7 @@ var should = require("should"),
 describe('batch.toBuffer arguments validation', function() {
 
     var batch;
-    before(function(done) {
+    beforeEach(function(done) {
         lwip.open(imgs.jpg.rgb, function(err, img) {
             batch = img.batch().blur(2);
             done(err);
@@ -50,36 +50,230 @@ describe('batch.toBuffer arguments validation', function() {
 
     describe('PNG params', function() {
 
-        describe('invalid compression - string', function() {
-            it('should throw an error', function() {
-                batch.toBuffer.bind(batch, 'png', {
-                    compression: 'foo'
-                }, function() {}).should.throwError();
+        describe("valid params", function(){
+
+            describe('defaults', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', done).should.not.throwError();
+                });
             });
-        });
 
-        describe('invalid compression - number', function() {
-            it('should throw an error', function() {
-                batch.toBuffer.bind(batch, 'png', {
-                    compression: 98
-                }, function() {}).should.throwError();
+            describe('none, false, true', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'none',
+                        interlaced: false,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
             });
-        });
 
-        describe('invalid interlaced - string', function() {
-            it('should throw an error', function() {
-                batch.toBuffer.bind(batch, 'png', {
-                    interlaced: 'foo'
-                }, function() {}).should.throwError();
+            describe('fast, false, true', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'fast',
+                        interlaced: false,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, false, true', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'high',
+                        interlaced: false,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, true, true', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'none',
+                        interlaced: true,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, true, true', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'fast',
+                        interlaced: true,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, true, true', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'high',
+                        interlaced: true,
+                        transparency: true
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, false, false', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'none',
+                        interlaced: false,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, false, false', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'fast',
+                        interlaced: false,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, false, false', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'high',
+                        interlaced: false,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, true, false', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'none',
+                        interlaced: true,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, true, false', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'fast',
+                        interlaced: true,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
             });
+
+            describe('high, true, false', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'high',
+                        interlaced: true,
+                        transparency: false
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, false, auto', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'none',
+                        interlaced: false,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, false, auto', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'fast',
+                        interlaced: false,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, false, auto', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'high',
+                        interlaced: false,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('none, true, auto', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'none',
+                        interlaced: true,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('fast, true, auto', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'fast',
+                        interlaced: true,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
+            describe('high, true, auto', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'high',
+                        interlaced: true,
+                        transparency: 'auto'
+                    }, done).should.not.throwError();
+                });
+            });
+
         });
 
-        describe('invalid interlaced - number', function() {
-            it('should throw an error', function() {
-                batch.toBuffer.bind(batch, 'png', {
-                    interlaced: 55
-                }, function() {}).should.throwError();
+        describe("invalid params", function(){
+
+            describe('invalid compression - string', function() {
+                it('should throw an error', function() {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 'foo'
+                    }, function() {}).should.throwError();
+                });
+            });
+
+            describe('invalid compression - number', function() {
+                it('should throw an error', function() {
+                    batch.toBuffer.bind(batch, 'png', {
+                        compression: 98
+                    }, function() {}).should.throwError();
+                });
+            });
+
+            describe('invalid interlaced - string', function() {
+                it('should throw an error', function() {
+                    batch.toBuffer.bind(batch, 'png', {
+                        interlaced: 'foo'
+                    }, function() {}).should.throwError();
+                });
             });
+
+            describe('invalid interlaced - number', function() {
+                it('should throw an error', function() {
+                    batch.toBuffer.bind(batch, 'png', {
+                        interlaced: 55
+                    }, function() {}).should.throwError();
+                });
+            });
+
         });
 
     });