diff --git a/sphinx/ext/graphviz.py b/sphinx/ext/graphviz.py
index a26e34fd5..800e9ca80 100644
--- a/sphinx/ext/graphviz.py
+++ b/sphinx/ext/graphviz.py
@@ -164,20 +164,13 @@ def render_dot(self, code, options, format, prefix='graphviz'):
                           self.builder.config.graphviz_dot)
         self.builder._graphviz_warned_dot = True
         return None, None
-    wentWrong = False
     try:
         # Graphviz may close standard input when an error occurs,
         # resulting in a broken pipe on communicate()
         stdout, stderr = p.communicate(code)
     except (OSError, IOError), err:
-        if err.errno != EPIPE:
+        if err.errno not in (EPIPE, EINVAL):
             raise
-        wentWrong = True
-    except IOError, err:
-        if err.errno != EINVAL:
-            raise
-        wentWrong = True
-    if wentWrong:
         # in this case, read the standard output and standard error streams
         # directly, to get the error message(s)
         stdout, stderr = p.stdout.read(), p.stderr.read()