diff --git a/shard.yml b/shard.yml
index 9a0c29e..193da67 100644
--- a/shard.yml
+++ b/shard.yml
@@ -1,5 +1,5 @@
 name: bacnet
-version: 0.9.0
+version: 0.9.1
 
 dependencies:
   bindata:
diff --git a/src/bacnet/ip4_message.cr b/src/bacnet/ip4_message.cr
index 6c8ff96..8b0965e 100644
--- a/src/bacnet/ip4_message.cr
+++ b/src/bacnet/ip4_message.cr
@@ -73,17 +73,17 @@ module BACnet
       end
     end
 
-    def to_io(io : IO, format : IO::ByteFormat = IO::ByteFormat::BigEndian) : IO
+    def to_io(io : IO, format : IO::ByteFormat = IO::ByteFormat::BigEndian) : Int64
       format = IO::ByteFormat::BigEndian
-      io.write_bytes(@data_link, format)
+      wrote = io.write_bytes(@data_link, format)
       if net = @network
-        io.write_bytes(net, format)
+        wrote += io.write_bytes(net, format)
         if app = @application
-          io.write_bytes(app, format)
-          objects.each { |object| io.write_bytes(object, format) }
+          wrote += io.write_bytes(app, format)
+          objects.each { |object| wrote += io.write_bytes(object, format) }
         end
       end
-      io
+      wrote
     end
 
     def to_slice
diff --git a/src/bacnet/secure_message.cr b/src/bacnet/secure_message.cr
index ed97be8..822f5ea 100644
--- a/src/bacnet/secure_message.cr
+++ b/src/bacnet/secure_message.cr
@@ -57,17 +57,17 @@ module BACnet
       end
     end
 
-    def to_io(io : IO, format : IO::ByteFormat = IO::ByteFormat::BigEndian) : IO
+    def to_io(io : IO, format : IO::ByteFormat = IO::ByteFormat::BigEndian) : Int64
       format = IO::ByteFormat::BigEndian
-      io.write_bytes(@data_link, format)
+      wrote = io.write_bytes(@data_link, format)
       if network = @network
-        io.write_bytes(network, format)
+        wrote += io.write_bytes(network, format)
         if app = @application
-          io.write_bytes(app, format)
-          objects.each { |object| io.write_bytes(object, format) }
+          wrote += io.write_bytes(app, format)
+          objects.each { |object| wrote += io.write_bytes(object, format) }
         end
       end
-      io
+      wrote
     end
 
     def to_slice