diff --git a/gunicorn/arbiter.py b/gunicorn/arbiter.py
index c73eb1f1..cb330d48 100644
--- a/gunicorn/arbiter.py
+++ b/gunicorn/arbiter.py
@@ -95,8 +95,10 @@ class Arbiter(object):
         self.pid = os.getpid()
         self.init_signals()
         self.LISTENER = create_socket(self.cfg)
-        self.pidfile = Pidfile(self.cfg.pidfile)
-        self.pidfile.create(self.pid)
+        
+        if self.cfg.pidfile is not None:
+            self.pidfile = Pidfile(self.cfg.pidfile)
+            self.pidfile.create(self.pid)
         self.log.info("Arbiter booted")
         self.log.info("Listening at: %s" % self.LISTENER)
         
diff --git a/gunicorn/pidfile.py b/gunicorn/pidfile.py
index 845d7427..8baa8878 100644
--- a/gunicorn/pidfile.py
+++ b/gunicorn/pidfile.py
@@ -32,7 +32,10 @@ class Pidfile(object):
         self.pid = pid
         
         # Write pidfile
-        fd, fname = tempfile.mkstemp(dir=os.path.dirname(self.fname))
+        fdir = os.path.dirname(self.fname)
+        if not os.path.isdir(fdir):
+            raise RuntimeError("%s don't exist. Can't create pidfile" % fdir)
+        fd, fname = tempfile.mkstemp(dir=fdir)
         os.write(fd, "%s\n" % self.pid)
         if self.fname:
             os.rename(fname, self.fname)