--- a/inst/pskdemod.m
+++ b/inst/pskdemod.m
@@ -22,8 +22,8 @@
 ## into an information sequence of integers in the range
 ## @code{[0 @dots{} M-1]}. @var{phi} controls the initial phase and
 ## @var{type} controls the constellation mapping. If @var{type} is set
-## to 'Bin' will result in binary encoding, in contrast, if set to
-## 'Gray' will give Gray encoding.  An example of Gray-encoded 8-PSK is
+## to "Bin" will result in binary encoding, in contrast, if set to
+## "Gray" will give Gray encoding.  An example of Gray-encoded 8-PSK is
 ##
 ## @example
 ## @group
@@ -66,5 +66,5 @@
 
 endfunction
 
-%!assert (pskdemod ([1 j -1 -j], 4, 0, 'Bin'), [0:3])
-%!assert (pskdemod ([1 j -j -1], 4, 0, 'Gray'), [0:3])
+%!assert (pskdemod ([1 j -1 -j], 4, 0, "Bin"), [0:3])
+%!assert (pskdemod ([1 j -j -1], 4, 0, "Gray"), [0:3])