diff -Nru netty-netty-3.10.6.Final/src/main/java/org/jboss/netty/handler/codec/compression/ZlibDecoder.java netty-netty-3.10.6.Final.jzlib/src/main/java/org/jboss/netty/handler/codec/compression/ZlibDecoder.java
--- netty-netty-3.10.6.Final/src/main/java/org/jboss/netty/handler/codec/compression/ZlibDecoder.java	2016-06-29 14:41:47.000000000 +0200
+++ netty-netty-3.10.6.Final.jzlib/src/main/java/org/jboss/netty/handler/codec/compression/ZlibDecoder.java	2016-11-03 15:51:13.967846143 +0100
@@ -77,7 +77,7 @@
 
         synchronized (z) {
             int resultCode;
-            resultCode = z.inflateInit(JZlib.W_ZLIB);
+            resultCode = z.inflateInit();
             if (resultCode != JZlib.Z_OK) {
                 ZlibUtil.fail(z, "initialization failure", resultCode);
             }
diff -Nru netty-netty-3.10.6.Final/src/main/java/org/jboss/netty/handler/codec/compression/ZlibEncoder.java netty-netty-3.10.6.Final.jzlib/src/main/java/org/jboss/netty/handler/codec/compression/ZlibEncoder.java
--- netty-netty-3.10.6.Final/src/main/java/org/jboss/netty/handler/codec/compression/ZlibEncoder.java	2016-06-29 14:41:47.000000000 +0200
+++ netty-netty-3.10.6.Final.jzlib/src/main/java/org/jboss/netty/handler/codec/compression/ZlibEncoder.java	2016-11-03 15:50:14.712839882 +0100
@@ -147,8 +147,7 @@
         wrapperOverhead = ZlibUtil.wrapperOverhead(wrapper);
 
         synchronized (z) {
-            int resultCode = z.deflateInit(compressionLevel, windowBits, memLevel,
-                    ZlibUtil.convertWrapperType(wrapper));
+            int resultCode = z.deflateInit(compressionLevel, ZlibUtil.convertWrapperType(wrapper), memLevel);
             if (resultCode != JZlib.Z_OK) {
                 ZlibUtil.fail(z, "initialization failure", resultCode);
             }
@@ -235,8 +234,7 @@
 
         synchronized (z) {
             int resultCode;
-            resultCode = z.deflateInit(compressionLevel, windowBits, memLevel,
-                    JZlib.W_ZLIB); // Default: ZLIB format
+            resultCode = z.deflateInit(compressionLevel, windowBits, memLevel);
             if (resultCode != JZlib.Z_OK) {
                 ZlibUtil.fail(z, "initialization failure", resultCode);
             } else {
diff -Nru netty-netty-3.10.6.Final/src/main/java/org/jboss/netty/handler/codec/compression/ZlibUtil.java netty-netty-3.10.6.Final.jzlib/src/main/java/org/jboss/netty/handler/codec/compression/ZlibUtil.java
--- netty-netty-3.10.6.Final/src/main/java/org/jboss/netty/handler/codec/compression/ZlibUtil.java	2016-06-29 14:41:47.000000000 +0200
+++ netty-netty-3.10.6.Final.jzlib/src/main/java/org/jboss/netty/handler/codec/compression/ZlibUtil.java	2016-11-03 15:48:56.294801795 +0100
@@ -32,25 +32,26 @@
                 (z.msg != null? ": " + z.msg : ""));
     }
 
-    static Enum<?> convertWrapperType(ZlibWrapper wrapper) {
-        Enum<?> convertedWrapperType;
-        switch (wrapper) {
+    static int convertWrapperType(ZlibWrapper wrapper, int windowBits) {
+      switch (wrapper) {
         case NONE:
-            convertedWrapperType = JZlib.W_NONE;
+            windowBits = -windowBits;
             break;
         case ZLIB:
-            convertedWrapperType = JZlib.W_ZLIB;
             break;
         case GZIP:
-            convertedWrapperType = JZlib.W_GZIP;
+            windowBits += 16;
             break;
         case ZLIB_OR_NONE:
-            convertedWrapperType = JZlib.W_ZLIB_OR_NONE;
             break;
         default:
             throw new Error();
         }
-        return convertedWrapperType;
+        return windowBits;
+    }
+
+    static int convertWrapperType(ZlibWrapper wrapper) {
+        return convertWrapperType(wrapper, 15);
     }
 
     static int wrapperOverhead(ZlibWrapper wrapper) {