diff --git a/matlab/set_observed_exogenous_variables.m b/matlab/set_observed_exogenous_variables.m
new file mode 100644
index 000000000..c9e350f78
--- /dev/null
+++ b/matlab/set_observed_exogenous_variables.m
@@ -0,0 +1,35 @@
+function DynareModel = set_observed_exogenous_variables(DynareModel)
+
+% Appends the list of observed exogenous variables in Dynare's model structure (if any).
+%
+% INPUTS
+% - DynareModel   [struct]    Dynare's model global structure, M_.
+%
+% OUTPUTS
+% - DynareModel   [struct]    Dynare's model global structure, M_.
+%
+% SPECIAL REQUIREMENTS
+%    none
+
+% Copyright (C) 2019 Dynare Team
+%
+% This file is part of Dynare.
+%
+% Dynare is free software: you can redistribute it and/or modify
+% it under the terms of the GNU General Public License as published by
+% the Free Software Foundation, either version 3 of the License, or
+% (at your option) any later version.
+%
+% Dynare is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
+
+if isfield(DynareModel, 'exo_partitions')
+    if isfield(DynareModel.exo_partitions, 'status')
+        DynareModel.observed_exo_names = DynareModel.exo_names(strcmpi('observed', DynareModel.exo_partitions.status));
+    end
+end
\ No newline at end of file
diff --git a/preprocessor b/preprocessor
index 9b1b4113d..556789abc 160000
--- a/preprocessor
+++ b/preprocessor
@@ -1 +1 @@
-Subproject commit 9b1b4113d9954c35f1c839f3657ff0b42f8fd6a9
+Subproject commit 556789abce78c36d79b4ce6f0781f96ce111c43b
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 4bdb53050..be1f1b7ea 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -432,6 +432,7 @@ MODFILES = \
     pac/trend-component-22/example.mod \
     pac/trend-component-23/example.mod \
     pac/trend-component-24/example.mod \
+    write/example1.mod \
     ecb/backward-models/irf/solow_1.mod \
     ecb/backward-models/irf/solow_2.mod \
 	dynare-command-options/ramst.mod
diff --git a/tests/write/example1.mod b/tests/write/example1.mod
new file mode 100644
index 000000000..8ba9f85a3
--- /dev/null
+++ b/tests/write/example1.mod
@@ -0,0 +1,89 @@
+// --+ options: json=compute, stochastic +--
+
+var x1 x2 x1bar x2bar z y x;
+
+varexo ex1
+       ex2
+       ex1bar
+       ex2bar
+       ez
+       ey   (status='observed') // This shock is observed...
+       ex   (status='observed') // ... this one also. Other shocks will be  considered as non observed.
+;
+
+parameters
+       rho_1 rho_2 rho_3 rho_4
+       a_x1_0 a_x1_1 a_x1_2 a_x1_x2_1 a_x1_x2_2
+	   a_x2_0 a_x2_1 a_x2_2 a_x2_x1_1 a_x2_x1_2
+	   e_c_m c_z_1 c_z_2 beta
+       lambda;
+
+rho_1 =  .9;
+rho_2 = -.2;
+rho_3 =  .4;
+rho_4 = -.3;
+
+
+a_x1_0 =  -.9;
+a_x1_1 =  .4;
+a_x1_2 =  .3;
+a_x1_x2_1 = .1;
+a_x1_x2_2 = .2;
+
+a_x2_0 =  -.9;
+a_x2_1 =   .2;
+a_x2_2 =  -.1;
+a_x2_x1_1 = -.1;
+a_x2_x1_2 = .2;
+
+beta  =  .2;
+e_c_m =  .5;
+c_z_1 =  .2;
+c_z_2 = -.1;
+
+lambda = 0.5; // Share of optimizing agents.
+
+trend_component_model(model_name=toto, eqtags=['eq:x1', 'eq:x2', 'eq:x1bar', 'eq:x2bar'], targets=['eq:x1bar', 'eq:x2bar']);
+
+pac_model(auxiliary_model_name=toto, discount=beta, model_name=pacman);
+
+model;
+
+[name='eq:y']
+y = rho_1*y(-1) + rho_2*y(-2) + ey;
+
+[name='eq:x']
+x = rho_3*x(-1) + rho_4*x(-2) + ex;
+
+[name='eq:x1']
+diff(x1) = a_x1_0*(x1(-1)-x1bar(-1)) + a_x1_1*diff(x1(-1)) + a_x1_2*diff(x1(-2)) + a_x1_x2_1*diff(x2(-1)) + a_x1_x2_2*diff(x2(-2)) + ex1;     
+
+[name='eq:x2']
+diff(x2) = a_x2_0*(x2(-1)-x2bar(-1)) + a_x2_1*diff(x1(-1)) + a_x2_2*diff(x1(-2)) + a_x2_x1_1*diff(x2(-1)) + a_x2_x1_2*diff(x2(-2)) + ex2;     
+
+[name='eq:x1bar']
+x1bar = x1bar(-1) + ex1bar;
+
+[name='eq:x2bar']
+x2bar = x2bar(-1) + ex2bar;
+
+[name='zpac']
+diff(z) = lambda*(e_c_m*(x1(-1)-z(-1)) + c_z_1*diff(z(-1))  + c_z_2*diff(z(-2)) + pac_expectation(pacman)) + (1-lambda)*( y + x) + ez;
+
+end;
+
+shocks;
+    var ex1 = 1.0;
+    var ex2 = 1.0;
+    var ex1bar = 1.0;
+    var ex2bar = 1.0;
+    var ez = 1.0;
+    var ey = 0.1;
+    var ex = 0.1;
+end;
+
+verbatim;
+  if ~isequal(M_.observed_exo_names, {'ey'; 'ex'})
+    error()
+  end
+end;