diff --git a/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java b/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
index a5490c3..38e8a19 100644
--- a/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
+++ b/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
@@ -1385,6 +1385,8 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
         switch(op) {
             case NEW:
             case NEW_DEFAULT:
+                codeStream.writeOpCode( RTT_CANON );
+                codeStream.writeValueType( type );
                 opCode = STRUCT_NEW;
                 break;
             case GET:
diff --git a/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java b/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java
index fea2862..03ef26e 100644
--- a/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java
+++ b/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java
@@ -487,22 +487,22 @@ interface InstructionOpcodes {
 
     static final int TABLE_FILL             = 0xFC11;
 
-    // === GC opcodes (unofficial, experimental) ===== https://github.com/lars-t-hansen/moz-gc-experiments/blob/master/version2.md
+    // === GC opcodes
 
-    static final int STRUCT_NEW             = 0xFC50;
+    static final int STRUCT_NEW             = 0xFB01;
 
-    static final int STRUCT_GET             = 0xFC51;
+    static final int STRUCT_GET             = 0xFB03;
 
-    static final int STRUCT_SET             = 0xFC52;
-
-    static final int STRUCT_NARROW          = 0xFC53;
+    static final int STRUCT_SET             = 0xFB06;
 
 
-    static final int ARRAY_NEW              = 0xFC60;
+    static final int ARRAY_NEW              = 0xFB11;
 
-    static final int ARRAY_GET              = 0xFC61;
+    static final int ARRAY_GET              = 0xFB13;
 
-    static final int ARRAY_SET              = 0xFC62;
+    static final int ARRAY_SET              = 0xFB16;
 
-    static final int ARRAY_LEN              = 0xFC63;
+    static final int ARRAY_LEN              = 0xFB17;
+
+    static final int RTT_CANON              = 0xFB30;
 }
diff --git a/src/de/inetsoftware/jwebassembly/binary/WasmOutputStream.java b/src/de/inetsoftware/jwebassembly/binary/WasmOutputStream.java
index 8106a40..629f4be 100644
--- a/src/de/inetsoftware/jwebassembly/binary/WasmOutputStream.java
+++ b/src/de/inetsoftware/jwebassembly/binary/WasmOutputStream.java
@@ -137,7 +137,7 @@ class WasmOutputStream extends LittleEndianOutputStream {
             }
         } else {
             writeOpCode( InstructionOpcodes.REF_NULL );
-            writeValueType( ValueType.externref );
+            writeValueType( type );
         }
     }
 
diff --git a/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java b/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java
index cc21ef3..477df19 100644
--- a/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java
+++ b/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java
@@ -852,6 +852,8 @@ public class TextModuleWriter extends ModuleWriter {
         switch( op ) {
             case NEW:
             case NEW_DEFAULT:
+                newline( methodOutput );
+                methodOutput.append( "rtt.canon" ).append( ' ' ).append( normalizeName( type.toString() ) );
                 operation = "struct.new";
                 break;
             case GET:
diff --git a/test/de/inetsoftware/jwebassembly/runtime/StructsGC.java b/test/de/inetsoftware/jwebassembly/runtime/StructsGC.java
index 76ba90b..ccc5798 100644
--- a/test/de/inetsoftware/jwebassembly/runtime/StructsGC.java
+++ b/test/de/inetsoftware/jwebassembly/runtime/StructsGC.java
@@ -39,7 +39,7 @@ public class StructsGC extends AbstractBaseTest {
     @Parameters( name = "{0}-{1}" )
     public static Collection<Object[]> data() {
         ArrayList<Object[]> list = new ArrayList<>();
-        ScriptEngine[] engines = { ScriptEngine.SpiderMonkeyGC, ScriptEngine.SpiderMonkeyWatGC, ScriptEngine.NodeJsGC, ScriptEngine.NodeWatGC };
+        ScriptEngine[] engines = { ScriptEngine.SpiderMonkeyGC, ScriptEngine.SpiderMonkeyWatGC, ScriptEngine.NodeJsGC/*, ScriptEngine.NodeWatGC*/ };
         for( ScriptEngine script : engines ) {
             addParam( list, script, "isNull" );
             addParam( list, script, "isNotNull" );
@@ -57,7 +57,7 @@ public class StructsGC extends AbstractBaseTest {
 
     @Test
     public void test() {
-        Assume.assumeFalse( true ); //TODO
+        Assume.assumeFalse( getScriptEngine().name().startsWith( "SpiderMonkey" ) ); //TODO
         super.test();
     }