diff --git a/src/@dates/setdiff.m b/src/@dates/setdiff.m
index 2417db0a1c2069fd2d436f67cd8de9acec7064c0..955de5194f572686a684a102f6f099ca2b994253 100644
--- a/src/@dates/setdiff.m
+++ b/src/@dates/setdiff.m
@@ -41,7 +41,7 @@ if isempty(p)
     return
 end
 
-if o==p
+if isequal(o.length(),p.length()) && isequal(o, p)
     % Return an empty dates object.
     q = dates(o.freq);
     if nargout>1, io = []; end