diff --git a/lib/preprocessor.js b/lib/preprocessor.js
index d1d1425c2..309310a51 100644
--- a/lib/preprocessor.js
+++ b/lib/preprocessor.js
@@ -1,3 +1,4 @@
+var path = require('path');
 var fs = require('graceful-fs');
 var crypto = require('crypto');
 var mm = require('minimatch');
@@ -10,12 +11,29 @@ var sha1 = function(data) {
   return hash.digest('hex');
 };
 
+var isBinary = Object.create(null);
+[
+  'adp', 'au', 'mid', 'mp4a', 'mpga', 'oga', 's3m', 'sil', 'eol', 'dra', 'dts', 'dtshd', 'lvp',
+  'pya', 'ecelp4800', 'ecelp7470', 'ecelp9600', 'rip', 'weba', 'aac', 'aif', 'caf', 'flac', 'mka',
+  'm3u', 'wax', 'wma', 'wav', 'xm', 'flac', '3gp', '3g2', 'h261', 'h263', 'h264', 'jpgv', 'jpm',
+  'mj2', 'mp4', 'mpeg', 'ogv', 'qt', 'uvh', 'uvm', 'uvp', 'uvs', 'dvb', 'fvt', 'mxu', 'pyv', 'uvu',
+  'viv', 'webm', 'f4v', 'fli', 'flv', 'm4v', 'mkv', 'mng', 'asf', 'vob', 'wm', 'wmv', 'wmx', 'wvx',
+  'movie', 'smv', 'ts', 'bmp', 'cgm', 'g3', 'gif', 'ief', 'jpg', 'jpeg', 'ktx', 'png', 'btif',
+  'sgi', 'svg', 'tiff', 'psd', 'uvi', 'sub', 'djvu', 'dwg', 'dxf', 'fbs', 'fpx', 'fst', 'mmr',
+  'rlc', 'mdi', 'wdp', 'npx', 'wbmp', 'xif', 'webp', '3ds', 'ras', 'cmx', 'fh', 'ico', 'pcx', 'pic',
+  'pnm', 'pbm', 'pgm', 'ppm', 'rgb', 'tga', 'xbm', 'xpm', 'xwd', 'zip', 'rar', 'tar', 'bz2', 'eot',
+  'ttf', 'woff'
+].forEach(function(extension) {
+  isBinary['.' + extension] = true;
+});
+
 // TODO(vojta): instantiate preprocessors at the start to show warnings immediately
 var createPreprocessor = function(config, basePath, injector) {
   var patterns = Object.keys(config);
   var alreadyDisplayedWarnings = Object.create(null);
 
   return function(file, done) {
+    var thisFileIsBinary = isBinary[path.extname(file.originalPath)];
     var preprocessors = [];
     var nextPreprocessor = function(error, content) {
       // normalize B-C
@@ -61,18 +79,17 @@ var createPreprocessor = function(config, basePath, injector) {
     // TODO(vojta): should we cache this ?
     for (var i = 0; i < patterns.length; i++) {
       if (mm(file.originalPath, patterns[i])) {
-        config[patterns[i]].forEach(instantiatePreprocessor);
+        if (thisFileIsBinary) {
+          log.warn('Ignoring preprocessing (%s) %s because it is a binary file.', config[patterns[i]].join(', '), file.originalPath);
+        } else {
+          config[patterns[i]].forEach(instantiatePreprocessor);
+        }
       }
     }
 
-    // compute SHA of the content
-    preprocessors.push(function(content, file, done) {
-      file.sha = sha1(content);
-      done(content);
-    });
-
     return fs.readFile(file.originalPath, function(err, buffer) {
-      nextPreprocessor(buffer.toString());
+      file.sha = sha1(buffer);
+      nextPreprocessor(null, thisFileIsBinary ? buffer : buffer.toString());
     });
   };
 };
diff --git a/test/unit/preprocessor.spec.coffee b/test/unit/preprocessor.spec.coffee
index ed77b6cc0..61dd224bc 100644
--- a/test/unit/preprocessor.spec.coffee
+++ b/test/unit/preprocessor.spec.coffee
@@ -12,6 +12,7 @@ describe 'preprocessor', ->
       some:
         'a.js': mocks.fs.file 0, 'content'
         'a.txt': mocks.fs.file 0, 'some-text'
+        'photo.png': mocks.fs.file 0, 'binary'
 
     mocks_ =
       'graceful-fs': mockFs
@@ -133,3 +134,21 @@ describe 'preprocessor', ->
     pp file, (err) ->
       expect(fakePreprocessor).not.to.have.been.called
       done()
+
+
+  it 'should not preprocess binary files', (done) ->
+    fakePreprocessor = sinon.spy (content, file, done) ->
+      done null, content
+
+    injector = new di.Injector [{
+      'preprocessor:fake': ['factory', -> fakePreprocessor]
+    }]
+
+    pp = m.createPreprocessor {'**/*': ['fake']}, null, injector
+
+    file = {originalPath: '/some/photo.png', path: 'path'}
+
+    pp file, (err) ->
+      expect(fakePreprocessor).not.to.have.been.called
+      expect(file.content).to.be.an.instanceof Buffer
+      done()