diff --git a/pyNN/common/control.py b/pyNN/common/control.py
index cafe6f525..af809f014 100644
--- a/pyNN/common/control.py
+++ b/pyNN/common/control.py
@@ -51,7 +51,11 @@ def setup(timestep=DEFAULT_TIMESTEP, min_delay=DEFAULT_MIN_DELAY,
             raise Exception("min_delay has to be less than or equal to max_delay.")
         if min_delay < timestep:
             raise Exception("min_delay (%g) must be greater than timestep (%g)" % (min_delay, timestep))
-
+        if timestep<0. or min_delay<0.:
+            raise Warning("Times are negative")
+    if min_delay == 'auto':
+        if timestep<0.:
+            raise Warning("Warning : Times are negative")
 
 def end(compatible_output=True):
     """Do any necessary cleaning up before exiting."""
diff --git a/pyNN/nest/__init__.py b/pyNN/nest/__init__.py
index fa8f37ffb..9d377b5b8 100644
--- a/pyNN/nest/__init__.py
+++ b/pyNN/nest/__init__.py
@@ -138,6 +138,9 @@ def setup(timestep=DEFAULT_TIMESTEP, min_delay=DEFAULT_MIN_DELAY,
     # Set min_delay and max_delay
     simulator.state.set_delays(min_delay, max_delay)
     nest.SetDefaults('spike_generator', {'precise_times': True})
+    if min_delay == 'auto':
+        print("Warning due to the parrot neuron which introduces an exra delay. 'min_delay' must be reduced")
+        return Warning("Warning due to the parrot neuron which introduces an exra delay. 'min_delay' must be reduced")
     return rank()
 
 
diff --git a/pyNN/nest/standardmodels/cells.py b/pyNN/nest/standardmodels/cells.py
index f57db9bf6..f67bcb4a5 100644
--- a/pyNN/nest/standardmodels/cells.py
+++ b/pyNN/nest/standardmodels/cells.py
@@ -289,7 +289,8 @@ def adjust_spike_times_forward(spike_times):
     parrot neuron.
     """
     # todo: emit warning if any times become negative
-    return spike_times - simulator.state.min_delay
+#    return spike_times - simulator.state.min_delay
+    return spike_times + simulator.state.min_delay
 
 
 def adjust_spike_times_backward(spike_times):
diff --git a/pyNN/parameters.py b/pyNN/parameters.py
index b5dd0e35d..6ff49f898 100644
--- a/pyNN/parameters.py
+++ b/pyNN/parameters.py
@@ -123,6 +123,8 @@ def __init__(self, value):
             self.value = value
         else:
             self.value = numpy.array(value, float)
+        if (self.value<0.).any(): 
+            print("Warning : Times are negative")
 
     # def __len__(self):
     #     This must not be defined, otherwise Sequence is insufficiently different from NumPy array