--- a/inst/randsrc.m
+++ b/inst/randsrc.m
@@ -102,7 +102,7 @@
 endfunction
 
 %!shared n, alph1, alph2, seed, a1, a2, a3, a4, a5, a6
-%!    n = 10; alph1 = [0, 1; 0.3, 0.7]; alph2 = ['a', 'b']; seed = 1;
+%!    n = 10; alph1 = [0, 1; 0.3, 0.7]; alph2 = ["a", "b"]; seed = 1;
 %!    a1 = randsrc (n); a2 = randsrc (n, n);
 %!    a3 = randsrc (n, n, alph1); a4 = randsrc (n, n, alph2);
 %!    a5 = randsrc (n, n, alph1, seed); a6 = randsrc (n, n, alph1, seed);
@@ -112,6 +112,6 @@
 %!assert (max ([a1(:); a2(:)]) <= 1 && min ([a1(:); a2(:)]) >= -1);
 %!assert (size (a3) == [n, n] && size (a4) == [n, n]);
 %!assert (max (a3(:)) <= 1 && min (a3(:)) >= 0);
-%!assert (max (toascii (a4(:))) <= toascii ('b'))
-%!assert (max (toascii (a4(:))) >= toascii ('a'))
+%!assert (max (toascii (a4(:))) <= toascii ("b"))
+%!assert (max (toascii (a4(:))) >= toascii ("a"))
 %!assert (a5(:) == a6(:));