diff --git a/lib/zlib.toit b/lib/zlib.toit
index 433179665..7aa457ce0 100644
--- a/lib/zlib.toit
+++ b/lib/zlib.toit
@@ -232,8 +232,8 @@ abstract class Coder_:
   signal_ /monitor.Signal := monitor.Signal
   state_/int := STATE_READY_TO_READ_ | STATE_READY_TO_WRITE_
 
-  static STATE_READY_TO_READ_ ::= 1
-  static STATE_READY_TO_WRITE_ ::= 2
+  static STATE_READY_TO_READ_  ::= 1 << 0
+  static STATE_READY_TO_WRITE_ ::= 1 << 1
 
   constructor .zlib_:
     reader = ZlibReader.private_
@@ -259,12 +259,12 @@ abstract class Coder_:
     return result
 
   close_read_ -> none:
-    state_ |= STATE_READY_TO_WRITE_
-    signal_.raise
     if not closed_read_:
       closed_read_ = true
       if closed_write_:
         uninit_
+      state_ |= STATE_READY_TO_WRITE_
+      signal_.raise
 
   write --wait/bool=true data -> int:
     if closed_read_: throw "READER_CLOSED"