diff --git a/matlab/dynare_config.m b/matlab/dynare_config.m
index 8d214fa49..75cbcb0a3 100644
--- a/matlab/dynare_config.m
+++ b/matlab/dynare_config.m
@@ -132,6 +132,11 @@ if ~isoctave && matlab_ver_less_than('7.11')
     p{end+1} = '/missing/is-row-column-matrix';
 end
 
+%% isdiag is missing in MATLAB < R2014a
+if ~isoctave && matlab_ver_less_than('8.4')
+    p{end+1} = '/missing/isdiag';
+end
+
 P = cellfun(@(c)[dynareroot(1:end-1) c], p, 'uni',false);
 
 % Get mex files folder(s)
diff --git a/matlab/imcforecast.m b/matlab/imcforecast.m
index 4760dfa1d..4b132c5dc 100644
--- a/matlab/imcforecast.m
+++ b/matlab/imcforecast.m
@@ -180,7 +180,7 @@ if options_.loglinear && isfield(oo_.dr,'ys') && options_.logged_steady_state==0
     options_.logged_steady_state=1; %set option for use in stoch_simul
 end
 
-if ~isdiagonal(M_.Sigma_e)
+if ~isdiag(M_.Sigma_e)
     warning(sprintf('The innovations are correlated (the covariance matrix has non zero off diagonal elements), the results of the conditional forecasts will\ndepend on the ordering of the innovations (as declared after varexo) because a Cholesky decomposition is used to factorize the covariance matrix.\n\n=> It is preferable to declare the correlations in the model block (explicitly imposing the identification restrictions), unless you are satisfied\nwith the implicit identification restrictions implied by the Cholesky decomposition.'))
     sQ = chol(M_.Sigma_e,'lower');
 else
@@ -299,4 +299,4 @@ forecasts.graph.fname = M_.fname;
 %reset qz_criterium
 options_.qz_criterium=qz_criterium_old;
 
-save('conditional_forecasts.mat','forecasts');
\ No newline at end of file
+save('conditional_forecasts.mat','forecasts');
diff --git a/matlab/utilities/general/isdiagonal.m b/matlab/missing/isdiag/isdiag.m
similarity index 82%
rename from matlab/utilities/general/isdiagonal.m
rename to matlab/missing/isdiag/isdiag.m
index a8c1a4cf8..89dcec2f1 100644
--- a/matlab/utilities/general/isdiagonal.m
+++ b/matlab/missing/isdiag/isdiag.m
@@ -1,4 +1,4 @@
-function b = isdiagonal(A) % --*-- Unitary tests --*--
+function b = isdiag(A) % --*-- Unitary tests --*--
 
 % Copyright (C) 2014-2017 Dynare Team
 %
@@ -25,38 +25,38 @@ if isnumeric(A)
         % in ir and ic (row and column numbers) should be equal.
         b = isequal(ir, ic);
     else
-        error('isdiagonal: Input must be a square matrix!')
+        error('isdiag: Input must be a square matrix!')
     end
 else
-    error('isdiagonal: Input must be numeric!')
+    error('isdiag: Input must be numeric!')
 end
 
 %@test:1
 %$ A = zeros(3,3);
-%$ t = isdiagonal(A);
+%$ t = isdiag(A);
 %$ T = all(t);
 %@eof:1
 
 %@test:2
 %$ A = zeros(3,3); A(1,3) = 1;
-%$ t = ~isdiagonal(A);
+%$ t = ~isdiag(A);
 %$ T = all(t);
 %@eof:2
 
 %@test:3
 %$ A = randn(3,3);
-%$ t = ~isdiagonal(A);
+%$ t = ~isdiag(A);
 %$ T = all(t);
 %@eof:3
 
 %@test:4
 %$ A = diag(randn(3,1));
-%$ t = isdiagonal(A);
+%$ t = isdiag(A);
 %$ T = all(t);
 %@eof:4
 
 %@test:5
 %$ A = diag(randn(3,1)); A(1,1) = 0;
-%$ t = isdiagonal(A);
+%$ t = isdiag(A);
 %$ T = all(t);
 %@eof:5