diff --git a/automat/_visualize.py b/automat/_visualize.py
index 05c020b..9468667 100644
--- a/automat/_visualize.py
+++ b/automat/_visualize.py
@@ -8,6 +8,46 @@
 from ._discover import findMachines
 
 
+FORMATS = frozenset([  # http://www.graphviz.org/doc/info/output.html
+    'bmp',
+    'canon', 'dot', 'gv', 'xdot', 'xdot1.2', 'xdot1.4',
+    'cgimage',
+    'cmap',
+    'eps',
+    'exr',
+    'fig',
+    'gd', 'gd2',
+    'gif',
+    'gtk',
+    'ico',
+    'imap', 'cmapx',
+    'imap_np', 'cmapx_np',
+    'ismap',
+    'jp2',
+    'jpg', 'jpeg', 'jpe',
+    'pct', 'pict',
+    'pdf',
+    'pic',
+    'plain', 'plain-ext',
+    'png',
+    'pov',
+    'ps',
+    'ps2',
+    'psd',
+    'sgi',
+    'svg', 'svgz',
+    'tga',
+    'tif', 'tiff',
+    'tk',
+    'vml', 'vmlz',
+    'vrml',
+    'wbmp',
+    'webp',
+    'xlib',
+    'x11',
+])
+
+
 def _gvquote(s):
     return '"{}"'.format(s.replace('"', r'\"'))
 
@@ -143,7 +183,7 @@ def tool(_progname=sys.argv[0],
                                 default=".automat_visualize")
     argumentParser.add_argument('--image-type', '-t',
                                 help="The image format.",
-                                choices=graphviz.files.FORMATS,
+                                choices=FORMATS,
                                 default='png')
     argumentParser.add_argument('--view', '-v',
                                 help="View rendered graphs with"