diff --git a/test/acceptance/ported/server_png8_format.js b/test/acceptance/ported/server_png8_format.js
index fdd5a131..39c89c66 100644
--- a/test/acceptance/ported/server_png8_format.js
+++ b/test/acceptance/ported/server_png8_format.js
@@ -108,7 +108,7 @@ describe('server_png8_format', function() {
                             assert.equal(responsePng8.headers['content-type'], "image/png");
                             bufferPng8 = responsePng8.body;
                             assert.ok(bufferPng8.length < bufferPng32.length);
-                            assert.imageBuffersAreEqual(bufferPng32, bufferPng8, IMAGE_EQUALS_TOLERANCE_PER_MIL,
+                            assert.imageBuffersAreSimilar(bufferPng32, bufferPng8, IMAGE_EQUALS_TOLERANCE_PER_MIL,
                                 function(err, imagePaths, similarity) {
 
                                     keysToDelete['map_cfg|' + LayergroupToken.parse(layergroupId).token] = 0;
diff --git a/test/support/assert.js b/test/support/assert.js
index a360ae3d..cf06e466 100644
--- a/test/support/assert.js
+++ b/test/support/assert.js
@@ -32,7 +32,7 @@ assert.imageEqualsFile = function(buffer, referenceImageRelativeFilePath, tolera
     assert.imagesAreSimilar(testImage, referenceImage, tolerance, callback);
 };
 
-assert.imageBuffersAreEqual = function(bufferA, bufferB, tolerance, callback) {
+assert.imageBuffersAreSimilar = function(bufferA, bufferB, tolerance, callback) {
     var testImage = mapnik.Image.fromBytes(Buffer.isBuffer(bufferA) ? bufferA : new Buffer(bufferA, 'binary'));
     var referenceImage = mapnik.Image.fromBytes(Buffer.isBuffer(bufferB) ? bufferB : new Buffer(bufferB, 'binary'));