il - readline function in .net assembler -

i'm trying figure il code out, cannot understand why next code crashed. when use same code without next row:call string [mscorlib]system.console::readline() code behavior expected, adding above described row force crash. what's wrong in statement??

.assembly hello {}     .method public static void somefunction() cil managed     {          .entrypoint          ldstr "hello, world!"          call void [mscorlib]system.console::writeline(string)          call string [mscorlib]system.console::readline()          ret     } 

readline returning string, guess there should "pop" before ret ?