Index: mttroot/mtt/bin/trans/m/mtt_optimise.m
==================================================================
--- mttroot/mtt/bin/trans/m/mtt_optimise.m
+++ mttroot/mtt/bin/trans/m/mtt_optimise.m
@@ -53,11 +53,11 @@
   theta = theta_0;
   Theta = [];
   Error = [];
   Y = [];
   iterations = 0;
-  while (abs(error_old-error)>criterion)&&(iterations<max_iterations)
+  while (abs(error_old-error)>criterion)&&(abs(error)>criterion)&&(iterations<max_iterations)
     iterations = iterations + 1;
     error_old_old = error_old;
     error_old = error;
     eval(sprintf("[t,y,y_theta] = \
 	mtt_s%s(system_name,theta,free);",method)); # Simulate system
@@ -88,11 +88,11 @@
       Theta = [Theta theta];	# Save parameters
       Y = [Y y];		# Save output
     endif
 
     ## Update the estimate if we are not done yet.
-    if (abs(error_old-error)>criterion)&&(iterations<max_iterations)
+    if (abs(error_old-error)>criterion)&&(abs(error)>criterion)&&(iterations<max_iterations)
       if error>(error_old+criterion) # Reduce step size and try again
         factor = 10;
 	disp(sprintf("%2.2f*step",alpha));
 	error = error_old;	# Go back to previous error value
 	error_old = inf;	# Don't let it think its converged