--- a/src/data.cc
+++ b/src/data.cc
@@ -1285,7 +1285,7 @@
         {
           octave_idx_type m = args(1).int_value (), n = args(2).int_value ();
           if (! error_state)
-            retval = arg0.diag ().resize (dim_vector (m, n));
+            retval = arg0.diag ().resize (dim_vector (m, n), true);
           else
             error ("diag: invalid dimensions");
         }
@@ -1299,44 +1299,49 @@
 }
 
 /*
-%!assert (full (diag ([1; 2; 3])), [1, 0, 0; 0, 2, 0; 0, 0, 3])
-%!assert (diag ([1; 2; 3], 1), [0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0])
-%!assert (diag ([1; 2; 3], 2), [0, 0, 1, 0, 0; 0, 0, 0, 2, 0; 0, 0, 0, 0, 3; 0, 0, 0, 0, 0; 0, 0, 0, 0, 0])
-%!assert (diag ([1; 2; 3],-1), [0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0])
-%!assert (diag ([1; 2; 3],-2), [0, 0, 0, 0, 0; 0, 0, 0, 0, 0; 1, 0, 0, 0, 0; 0, 2, 0, 0, 0; 0, 0, 3, 0, 0])
-
-%!assert (diag ([1, 0, 0; 0, 2, 0; 0, 0, 3]), [1; 2; 3])
-%!assert (diag ([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0], 1), [1; 2; 3])
-%!assert (diag ([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0], -1), [1; 2; 3])
-%!assert (diag (ones (1, 0), 2), zeros (2))
-%!assert (diag (1:3, 4, 2), [1, 0; 0, 2; 0, 0; 0, 0])
-
-%!assert (full (diag (single ([1; 2; 3]))), single ([1, 0, 0; 0, 2, 0; 0, 0, 3]))
-%!assert (diag (single ([1; 2; 3]), 1), single ([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0]))
-%!assert (diag (single ([1; 2; 3]), 2), single ([0, 0, 1, 0, 0; 0, 0, 0, 2, 0; 0, 0, 0, 0, 3; 0, 0, 0, 0, 0; 0, 0, 0, 0, 0]))
-%!assert (diag (single ([1; 2; 3]),-1), single ([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0]))
-%!assert (diag (single ([1; 2; 3]),-2), single ([0, 0, 0, 0, 0; 0, 0, 0, 0, 0; 1, 0, 0, 0, 0; 0, 2, 0, 0, 0; 0, 0, 3, 0, 0]))
-
-%!assert (diag (single ([1, 0, 0; 0, 2, 0; 0, 0, 3])), single ([1; 2; 3]))
-%!assert (diag (single ([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0]), 1), single ([1; 2; 3]))
-%!assert (diag (single ([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0]), -1), single ([1; 2; 3]))
-
-%!assert (diag (int8 ([1; 2; 3])), int8 ([1, 0, 0; 0, 2, 0; 0, 0, 3]))
-%!assert (diag (int8 ([1; 2; 3]), 1), int8 ([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0]))
-%!assert (diag (int8 ([1; 2; 3]), 2), int8 ([0, 0, 1, 0, 0; 0, 0, 0, 2, 0; 0, 0, 0, 0, 3; 0, 0, 0, 0, 0; 0, 0, 0, 0, 0]))
-%!assert (diag (int8 ([1; 2; 3]),-1), int8 ([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0]))
-%!assert (diag (int8 ([1; 2; 3]),-2), int8 ([0, 0, 0, 0, 0; 0, 0, 0, 0, 0; 1, 0, 0, 0, 0; 0, 2, 0, 0, 0; 0, 0, 3, 0, 0]))
-
-%!assert (diag (int8 ([1, 0, 0; 0, 2, 0; 0, 0, 3])), int8 ([1; 2; 3]))
-%!assert (diag (int8 ([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0]), 1), int8 ([1; 2; 3]))
-%!assert (diag (int8 ([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0]), -1), int8 ([1; 2; 3]))
-
-## Test input validation
-%!error diag ()
-%!error diag (1,2,3,4)
+
+%!assert(full (diag ([1; 2; 3])), [1, 0, 0; 0, 2, 0; 0, 0, 3])
+%!assert(diag ([1; 2; 3], 1), [0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0])
+%!assert(diag ([1; 2; 3], 2), [0, 0, 1, 0, 0; 0, 0, 0, 2, 0; 0, 0, 0, 0, 3; 0, 0, 0, 0, 0; 0, 0, 0, 0, 0])
+%!assert(diag ([1; 2; 3],-1), [0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0])
+%!assert(diag ([1; 2; 3],-2), [0, 0, 0, 0, 0; 0, 0, 0, 0, 0; 1, 0, 0, 0, 0; 0, 2, 0, 0, 0; 0, 0, 3, 0, 0])
+
+%!assert(diag ([1, 0, 0; 0, 2, 0; 0, 0, 3]), [1; 2; 3])
+%!assert(diag ([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0], 1), [1; 2; 3])
+%!assert(diag ([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0], -1), [1; 2; 3])
+%!assert(diag (ones(1, 0), 2), zeros (2))
+%!assert(diag (1:3, 4, 2), [1, 0; 0, 2; 0, 0; 0, 0])
+
+%!assert(full (diag (single([1; 2; 3]))), single([1, 0, 0; 0, 2, 0; 0, 0, 3]))
+%!assert(diag (single([1; 2; 3]), 1), single([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0]))
+%!assert(diag (single([1; 2; 3]), 2), single([0, 0, 1, 0, 0; 0, 0, 0, 2, 0; 0, 0, 0, 0, 3; 0, 0, 0, 0, 0; 0, 0, 0, 0, 0]))
+%!assert(diag (single([1; 2; 3]),-1), single([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0]))
+%!assert(diag (single([1; 2; 3]),-2), single([0, 0, 0, 0, 0; 0, 0, 0, 0, 0; 1, 0, 0, 0, 0; 0, 2, 0, 0, 0; 0, 0, 3, 0, 0]))
+
+%!assert(diag (single([1, 0, 0; 0, 2, 0; 0, 0, 3])), single([1; 2; 3]))
+%!assert(diag (single([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0]), 1), single([1; 2; 3]))
+%!assert(diag (single([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0]), -1), single([1; 2; 3]))
+
+%!assert(diag (int8([1; 2; 3])), int8([1, 0, 0; 0, 2, 0; 0, 0, 3]))
+%!assert(diag (int8([1; 2; 3]), 1), int8([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0]))
+%!assert(diag (int8([1; 2; 3]), 2), int8([0, 0, 1, 0, 0; 0, 0, 0, 2, 0; 0, 0, 0, 0, 3; 0, 0, 0, 0, 0; 0, 0, 0, 0, 0]))
+%!assert(diag (int8([1; 2; 3]),-1), int8([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0]))
+%!assert(diag (int8([1; 2; 3]),-2), int8([0, 0, 0, 0, 0; 0, 0, 0, 0, 0; 1, 0, 0, 0, 0; 0, 2, 0, 0, 0; 0, 0, 3, 0, 0]))
+
+%!assert(diag (int8([1, 0, 0; 0, 2, 0; 0, 0, 3])), int8([1; 2; 3]))
+%!assert(diag (int8([0, 1, 0, 0; 0, 0, 2, 0; 0, 0, 0, 3; 0, 0, 0, 0]), 1), int8([1; 2; 3]))
+%!assert(diag (int8([0, 0, 0, 0; 1, 0, 0, 0; 0, 2, 0, 0; 0, 0, 3, 0]), -1), int8([1; 2; 3]))
+
+## Test non-square size
+%!assert(diag ([1,2,3], 6, 3), [1 0 0; 0 2 0; 0 0 3; 0 0 0; 0 0 0; 0 0 0])
+
+%% Test input validation
+%!error <Invalid call to diag> diag ()
+%!error <Invalid call to diag> diag (1,2,3,4)
 %!error diag (ones (2), 3, 3)
 %!error diag (1:3, -4, 3)
-*/
+
+ */
 
 DEFUN (prod, args, ,
   "-*- texinfo -*-\n\