diff --git a/blimp.nim b/blimp.nim
index 9106a25..7b2a10a 100644
--- a/blimp.nim
+++ b/blimp.nim
@@ -127,6 +127,21 @@ proc expandDirs(templ: string): string =
     if gitRootDir.isNil: quit("Not in a git clone, can not expand %gitroot% in '" & templ & "'") 
     result = result.replace("%gitroot%", gitRootDir)
 
+# Copy of readAllBuffer from sysio.nim - we need to call it
+# instead of readAll(stdin) which doesn't work on Windows. readAll
+# first tries to find file size, and that trips up Windows.
+proc readAllX(file: File): string =
+  result = ""
+  var buffer = newString(4096)
+  while true:
+    var read = readBuffer(file, addr(buffer[0]), 4096)
+    if read == 4096:
+      result.add(buffer)
+    else:
+      buffer.setLen(read)
+      result.add(buffer)
+      break
+
 # Load a blimp.conf file
 proc parseConfFile(filename: string) =
   var f = newFileStream(filename, fmRead)
@@ -495,7 +510,7 @@ area = args["area"].asString
 if stdio:
   verbose = false
   try:
-    stdinContent = readAll(stdin)
+    stdinContent = readAllX(stdin)
     close(stdin)
   except:
     quit("Failed reading stdin", 1)