diff --git a/matlab/utilities/dates/isdate.m b/matlab/utilities/dates/isdate.m
index 82c02d840..ebcd2816e 100644
--- a/matlab/utilities/dates/isdate.m
+++ b/matlab/utilities/dates/isdate.m
@@ -25,7 +25,11 @@ function b = isdate(str)  % --*-- Unitary tests --*--
 % You should have received a copy of the GNU General Public License
 % along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
 
-b = isquaterly(str) || isyearly(str) || ismonthly(str) || isweekly(str);
+if length(str)>1
+    b = isquaterly(str) || isyearly(str) || ismonthly(str) || isweekly(str);
+else
+    b = 0;
+end
 
 %@test:1
 %$