diff --git a/extra/io/unix/backend/backend.factor b/extra/io/unix/backend/backend.factor
index 2128142615..7f130fc7e3 100755
--- a/extra/io/unix/backend/backend.factor
+++ b/extra/io/unix/backend/backend.factor
@@ -168,7 +168,7 @@ M: stdin dispose
 
 : wait-for-stdin ( stdin -- n )
     [ control>> CHAR: X over io:stream-write1 io:stream-flush ]
-    [ size>> "uint" heap-size swap io:stream-read *uint ]
+    [ size>> "size_t" heap-size swap io:stream-read *uint ]
     bi ;
 
 :: refill-stdin ( buffer stdin size -- )