diff --git a/lib/io/stream/generic.rb b/lib/io/stream/generic.rb
index ce64c7f..b21d3bf 100644
--- a/lib/io/stream/generic.rb
+++ b/lib/io/stream/generic.rb
@@ -154,7 +154,7 @@ def write(string, flush: false)
 			@writing.synchronize do
 				@write_buffer << string
 				
-				flush |= @write_buffer.bytesize >= @block_size
+				flush |= (@write_buffer.bytesize >= @block_size)
 				
 				if flush
 					self.drain(@write_buffer)