IO.read fails to return complete file content on windows ruby 1.9.3p448

stdout.txt

IO.read length: 1778
IO.binread length: 2395
next character after read_string: "\x1A"
context after read_string: "TI\"\x0FC:\\Windows\x06;\x00TI\"\x1Awindows_tracing_fla"
test.rb:60:in `load': marshal data too short (ArgumentError)
        from test.rb:60:in `<main>'

test_case.rb

# encoding: utf-8
config = {
  "argv"=>"git fetch", 
  "env"=>{
  "LC_ALL"=>"C",
  "APPDATA"=>"C:\\Windows\\system32\\config\\systemprofile\\AppData\\Roaming",
  "CommonProgramFiles"=>"C:\\Program Files (x86)\\Common Files",
  "CommonProgramFiles(x86)"=>"C:\\Program Files (x86)\\Common Files",
  "CommonProgramW6432"=>"C:\\Program Files\\Common Files",
  "COMPUTERNAME"=>"MO-FA64184F8",
  "ComSpec"=>"C:\\Windows\\system32\\cmd.exe",
  "FP_NO_HOST_CHECK"=>"NO",
  "HOME"=>"C:/Windows/system32/config/systemprofile",
  "LOCALAPPDATA"=>"C:\\Windows\\system32\\config\\systemprofile\\AppData\\Local",
  "NUMBER_OF_PROCESSORS"=>"4",
  "OS"=>"Windows_NT",
  "Path"=>"C:\\Program Files (x86)\\Git\\Cmd;C:\\Windows\\system32;C:\\Windows;C:\\Windows\\System32\\Wbem;C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\;C:\\opscode\\chef\\bin;C:\\opscode\\chef\\embedded\\bin;",
  "PATHEXT"=>".COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC",
  "PROCESSOR_ARCHITECTURE"=>"x86",
  "PROCESSOR_ARCHITEW6432"=>"AMD64",
  "PROCESSOR_IDENTIFIER"=>"Intel64 Family 6 Model 47 Stepping 2, GenuineIntel",
  "PROCESSOR_LEVEL"=>"6",
  "PROCESSOR_REVISION"=>"2f02",
  "ProgramData"=>"C:\\ProgramData",
  "ProgramFiles"=>"C:\\Program Files (x86)",
  "ProgramFiles(x86)"=>"C:\\Program Files (x86)",
  "ProgramW6432"=>"C:\\Program Files",
  "PSModulePath"=>"C:\\Windows\\system32\\WindowsPowerShell\\v1.0\\Modules\\",
  "PUBLIC"=>"C:\\Users\\Public",
  "SystemDrive"=>"C:",
  "SystemRoot"=>"C:\\Windows",
  "TEMP"=>"C:\\Windows\\TEMP",
  "TMP"=>"C:\\Windows\\TEMP",
  "USER"=>"MO-FA64184F8$",
  "USERDOMAIN"=>"WORKGROUP",
  "USERNAME"=>"MO-FA64184F8$",
  "USERPROFILE"=>"C:\\Windows\\system32\\config\\systemprofile",
  "windir"=>"C:\\Windows",
  "windows_tracing_flags"=>"3",
  "windows_tracing_logfile"=>"C:\\BVTBin\\Tests\\installpackage\\csilogfile.log",
  "GIT_SSH"=>"C:/blafasel/git_ssh.bat",
  "SYSTEMU_TURD"=>"X"
  },
  "cwd"=>"/var/lib/blafasel/repos/devel/mcollective",
  "stdin"=>"C:/Windows/Temp/systemu_mo-fa64184f8_540_3960_0.1555892908668568_1/stdin",
  "stdout"=>"C:/Windows/Temp/systemu_mo-fa64184f8_540_3960_0.1555892908668568_1/stdout",
  "stderr"=>"C:/Windows/Temp/systemu_mo-fa64184f8_540_3960_0.1555892908668568_1/stderr",
  "program"=>"C:/Windows/Temp/systemu_mo-fa64184f8_540_3960_0.1555892908668568_1/program"
 }

open('dump', 'wb') {|f|Marshal.dump config, f}

read_string = IO.read('dump')
binread_string = IO.binread('dump')

puts "IO.read length: #{read_string.length}"
puts "IO.binread length: #{binread_string.length}"
puts "next character after read_string end: #{binread_string[read_string.length].inspect}"
puts "context around read_string end: #{binread_string[read_string.length-20,40].inspect}"
Marshal.load IO.read('dump')