diff --git a/matlab/lmmcp/catstruct.m b/matlab/lmmcp/catstruct.m
index 8248366e43c1fb456bdb0642b1f7c4fcce59429d..e29d36469528262d70faa77445cedb18ffae78c4 100644
--- a/matlab/lmmcp/catstruct.m
+++ b/matlab/lmmcp/catstruct.m
@@ -124,7 +124,7 @@ else
     FN = squeeze(FN) ;
     VAL = squeeze(VAL) ;
     MatlabVersion = version;
-    if str2double(MatlabVersion(end-5:end-2))<2013 % Equivalent to, but faster than if verLessThan('matlab','8.1')
+    if isoctave || str2double(MatlabVersion(end-5:end-2))<2013 % Equivalent to, but faster than if verLessThan('matlab','8.1')
       [UFN,ind] = unique(FN) ;          
     else
       [UFN,ind] = unique(FN,'legacy') ;