--- a/scripts/plot/plotyy.m
+++ b/scripts/plot/plotyy.m
@@ -79,7 +79,7 @@
     ca = get (f, "currentaxes");
     if (isempty (ca))
       ax = [];
-    elseif (strcmp (get (ca, "tag"), "plotyy"))
+    elseif (ishandle (ca) && isprop (ca, "__plotyy_axes__"))
       ax = get (ca, "__plotyy_axes__");
     else
       ax = ca;
@@ -209,25 +209,21 @@
   addlistener (ax(1), "plotboxaspectratiomode", {@update_position, ax(2)});
   addlistener (ax(2), "plotboxaspectratiomode", {@update_position, ax(1)});
 
-  ## Tag the plotyy axes, so we can use that information
-  ## not to mirror the y axis tick marks
-  set (ax, "tag", "plotyy");
-
-  ## Cross-reference one axis to the other in the userdata
-  set (ax(1), "userdata", ax(2));
-  set (ax(2), "userdata", ax(1));
-
   ## Store the axes handles for the sister axes.
-  try
+  if (ishandle (ax(1)) && ! isprop (ax(1), "__plotyy_axes__"))
     addproperty ("__plotyy_axes__", ax(1), "data", ax);
-  catch
+  elseif (ishandle (ax(1)))
     set (ax(1), "__plotyy_axes__", ax);
-  end_try_catch
-  try
+  else
+    error ("plotyy.m: This shouldn't happen. File a bug report.")
+  endif
+  if (ishandle (ax(2)) && ! isprop (ax(2), "__plotyy_axes__"))
     addproperty ("__plotyy_axes__", ax(2), "data", ax);
-  catch
+  elseif (ishandle (ax(2)))
     set (ax(2), "__plotyy_axes__", ax);
-  end_try_catch
+  else
+    error ("plotyy.m: This shouldn't happen. File a bug report.")
+  endif
 endfunction
 
 %!demo