diff --git a/tftpy/TftpServer.py b/tftpy/TftpServer.py
index 95ca70e..686b6ad 100644
--- a/tftpy/TftpServer.py
+++ b/tftpy/TftpServer.py
@@ -42,7 +42,10 @@ def __init__(self,
         self.listenport = None
         self.sock = None
         # FIXME: What about multiple roots?
-        self.root = os.path.abspath(tftproot)
+        if tftproot != None:
+            self.root = os.path.abspath(tftproot)
+        else:
+            self.root = None
         self.dyn_file_func = dyn_file_func
         self.upload_open = upload_open
         # A dict of sessions, where each session is keyed by a string like
@@ -59,22 +62,26 @@ def __init__(self,
             attr = getattr(self, name)
             if attr and not callable(attr):
                 raise TftpException("{} supplied, but it is not callable.".format(name))
-        if os.path.exists(self.root):
-            log.debug("tftproot %s does exist", self.root)
-            if not os.path.isdir(self.root):
-                raise TftpException("The tftproot must be a directory.")
-            else:
-                log.debug("tftproot %s is a directory" % self.root)
-                if os.access(self.root, os.R_OK):
-                    log.debug("tftproot %s is readable" % self.root)
-                else:
-                    raise TftpException("The tftproot must be readable")
-                if os.access(self.root, os.W_OK):
-                    log.debug("tftproot %s is writable" % self.root)
+        if self.root != None:
+            if os.path.exists(self.root):
+                log.debug("tftproot %s does exist", self.root)
+                if not os.path.isdir(self.root):
+                    raise TftpException("The tftproot must be a directory.")
                 else:
-                    log.warning("The tftproot %s is not writable" % self.root)
+                    log.debug("tftproot %s is a directory" % self.root)
+                    if os.access(self.root, os.R_OK):
+                        log.debug("tftproot %s is readable" % self.root)
+                    else:
+                        raise TftpException("The tftproot must be readable")
+                    if os.access(self.root, os.W_OK):
+                        log.debug("tftproot %s is writable" % self.root)
+                    else:
+                        log.warning("The tftproot %s is not writable" % self.root)
+            else:
+                raise TftpException("The tftproot does not exist.")
         else:
-            raise TftpException("The tftproot does not exist.")
+            if dyn_file_func == None:
+                raise TftpException("No tftproot and no dyn_file_func given")
 
     def listen(self, listenip="", listenport=DEF_TFTP_PORT,
                timeout=SOCK_TIMEOUT):
diff --git a/tftpy/TftpStates.py b/tftpy/TftpStates.py
index 42bac1d..a7530b2 100644
--- a/tftpy/TftpStates.py
+++ b/tftpy/TftpStates.py
@@ -258,33 +258,33 @@ def serverInitial(self, pkt, raddress, rport):
 
         log.debug("Requested filename is %s", pkt.filename)
 
-        # Build the filename on this server and ensure it is contained
-        # in the specified root directory.
-        #
-        # Filenames that begin with server root are accepted. It's
-        # assumed the client and server are tightly connected and this
-        # provides backwards compatibility.
-        #
-        # Filenames otherwise are relative to the server root. If they
-        # begin with a '/' strip it off as otherwise os.path.join will
-        # treat it as absolute (regardless of whether it is ntpath or
-        # posixpath module
-        if pkt.filename.startswith(self.context.root):
-            full_path = pkt.filename
-        else:
-            full_path = os.path.join(self.context.root, pkt.filename.lstrip('/'))
-
-        # Use abspath to eliminate any remaining relative elements
-        # (e.g. '..') and ensure that is still within the server's
-        # root directory
-        self.full_path = os.path.abspath(full_path)
-        log.debug("full_path is %s", full_path)
-        if self.full_path.startswith(self.context.root):
-            log.info("requested file is in the server root - good")
-        else:
-            log.warning("requested file is not within the server root - bad")
-            self.sendError(TftpErrors.IllegalTftpOp)
-            raise TftpException("bad file path")
+        if self.context.root != None:
+            # Build the filename on this server and ensure it is contained
+            # in the specified root directory.
+            #
+            # Filenames that begin with server root are accepted. It's
+            # assumed the client and server are tightly connected and this
+            # provides backwards compatibility.
+            #
+            # Filenames otherwise are relative to the server root. If they
+            # begin with a '/' strip it off as otherwise os.path.join will
+            # treat it as absolute (regardless of whether it is ntpath or
+            # posixpath module
+            if pkt.filename.startswith(self.context.root):
+                full_path = pkt.filename
+            else:
+                full_path = os.path.join(self.context.root, pkt.filename.lstrip('/'))
+            # Use abspath to eliminate any remaining relative elements
+            # (e.g. '..') and ensure that is still within the server's
+            # root directory
+            self.full_path = os.path.abspath(full_path)
+            log.debug("full_path is %s", full_path)
+            if self.full_path.startswith(self.context.root):
+                log.info("requested file is in the server root - good")
+            else:
+                log.warning("requested file is not within the server root - bad")
+                self.sendError(TftpErrors.IllegalTftpOp)
+                raise TftpException("bad file path")
 
         self.context.file_to_transfer = pkt.filename
 
@@ -300,7 +300,7 @@ def handle(self, pkt, raddress, rport):
         sendoack = self.serverInitial(pkt, raddress, rport)
         path = self.full_path
         log.info("Opening file %s for reading" % path)
-        if os.path.exists(path):
+        if path != None and os.path.exists(path):
             # Note: Open in binary mode for win32 portability, since win32
             # blows.
             self.context.fileobj = open(path, "rb")