diff --git a/method/buffers.py b/method/buffers.py
index 335c2f5..b99e1cf 100644
--- a/method/buffers.py
+++ b/method/buffers.py
@@ -57,8 +57,11 @@ class KillBuffer(Method):
                  dv=default.current_buffer, h="name of the buffer to kill")]
     def _execute(self, w, **vargs):
         name = vargs['buffername']
-        a  = w.application
-        assert name in a.bufferlist.buffer_names, "Buffer %r does not exist" % name
+        a    = w.application
+        if name not in a.bufferlist.buffer_names:
+            raise Exception("Buffer %r does not exist" % name)
+        elif len(a.bufferlist.buffers) == 1:
+            raise Exception("Can't close only open buffer")
         self._to_kill    = a.bufferlist.buffer_names[name]
         self._old_window = w
         if self.force or not self._to_kill.changed():
diff --git a/mode/__init__.py b/mode/__init__.py
index 0ab1551..c54726e 100644
--- a/mode/__init__.py
+++ b/mode/__init__.py
@@ -461,8 +461,7 @@ class Fundamental(Handler):
             if DEBUG:
                 raise
             else:
-                err = "%s in mode '%s'" % (e, self.name)
-                self.window.set_error(err)
+                self.window.set_error(str(e))
 
     def region_added(self, p, newlines):
         mname = self.name