@@ -357,7 +357,7 @@ def _update_params(self, params, warning=False):
         if warning:
             warn("Parameters passed to InputOutputSystem ignored.")
 
-    def _rhs(self, t, x, u, params={}):
+    def _rhs(self, t, x, u):
         """Evaluate right hand side of a differential or difference equation.
 
         Private function used to compute the right hand side of an
@@ -369,7 +369,7 @@ def _rhs(self, t, x, u, params={}):
         NotImplemented("Evaluation not implemented for system of type ",
                        type(self))
 
-    def dynamics(self, t, x, u):
+    def dynamics(self, t, x, u, params={}):
         """Compute the dynamics of a differential or difference equation.
 
         Given time `t`, input `u` and state `x`, returns the value of the
@@ -400,9 +400,10 @@ def dynamics(self, t, x, u):
         -------
         dx/dt or x[t+dt] : ndarray
         """
+        self._update_params(params)
         return self._rhs(t, x, u)
 
-    def _out(self, t, x, u, params={}):
+    def _out(self, t, x, u):
         """Evaluate the output of a system at a given state, input, and time
 
         Private function used to compute the output of of an input/output
@@ -414,7 +415,7 @@ def _out(self, t, x, u, params={}):
         # If no output function was defined in subclass, return state
         return x
 
-    def output(self, t, x, u):
+    def output(self, t, x, u, params={}):
         """Compute the output of the system
 
         Given time `t`, input `u` and state `x`, returns the output of the
@@ -437,6 +438,7 @@ def output(self, t, x, u):
         -------
         y : ndarray
         """
+        self._update_params(params)
         return self._out(t, x, u)
 
     def feedback(self, other=1, sign=-1, params={}):
@@ -2248,7 +2250,7 @@ def ss(*args, **kwargs):
         Convert a linear system into space system form. Always creates a
         new system, even if sys is already a state space system.
 
-    ``ss(updfcn, outfucn)``
+    ``ss(updfcn, outfcn)``
         Create a nonlinear input/output system with update function ``updfcn``
         and output function ``outfcn``.  See :class:`NonlinearIOSystem` for
         more information.
 
@@ -19,7 +19,9 @@ def sys_dict():
     sdict['frd'] = ct.frd([10+0j, 9 + 1j, 8 + 2j, 7 + 3j], [1, 2, 3, 4])
     sdict['lio'] = ct.LinearIOSystem(ct.ss([[-1]], [[5]], [[5]], [[0]]))
     sdict['ios'] = ct.NonlinearIOSystem(
-        sdict['lio']._rhs, sdict['lio']._out, inputs=1, outputs=1, states=1)
+        lambda t, x, u, params: sdict['lio']._rhs(t, x, u),
+        lambda t, x, u, params: sdict['lio']._out(t, x, u),
+        inputs=1, outputs=1, states=1)
     sdict['arr'] = np.array([[2.0]])
     sdict['flt'] = 3.
     return sdict
@@ -226,4 +228,12 @@ def test_interconnect(
             result = ct.interconnect(syslist, connections, inplist, outlist)
     else:
             result = ct.interconnect(syslist, connections, inplist, outlist)
+
+            # Make sure the type is correct
             assert isinstance(result, type_dict[expected])
+
+            # Make sure we can evaluate the dynamics
+            np.testing.assert_equal(
+                result.dynamics(
+                    0, np.zeros(result.nstates), np.zeros(result.ninputs)),
+                np.zeros(result.nstates))