diff --git a/dom/base/StructuredCloneHolder.cpp b/dom/base/StructuredCloneHolder.cpp
index 9e725f0470f7..31e2d521263b 100644
--- a/dom/base/StructuredCloneHolder.cpp
+++ b/dom/base/StructuredCloneHolder.cpp
@@ -997,6 +997,41 @@ WriteFormData(JSStructuredCloneWriter* aWriter,
   return aFormData->ForEach(Closure::Write, &closure);
 }
 
+JSObject*
+ReadWasmModule(JSContext* aCx,
+               uint32_t aIndex,
+               StructuredCloneHolder* aHolder)
+{
+  MOZ_ASSERT(aHolder);
+  MOZ_ASSERT(aIndex < aHolder->WasmModules().Length());
+  MOZ_ASSERT(aHolder->CloneScope() == StructuredCloneHolder::StructuredCloneScope::SameProcessSameThread ||
+             aHolder->CloneScope() == StructuredCloneHolder::StructuredCloneScope::SameProcessDifferentThread);
+
+  RefPtr<JS::WasmModule> wasmModule = aHolder->WasmModules()[aIndex];
+  return wasmModule->createObject(aCx);
+}
+
+bool
+WriteWasmModule(JSStructuredCloneWriter* aWriter,
+                JS::WasmModule* aWasmModule,
+                StructuredCloneHolder* aHolder)
+{
+  MOZ_ASSERT(aWriter);
+  MOZ_ASSERT(aWasmModule);
+  MOZ_ASSERT(aHolder);
+  MOZ_ASSERT(aHolder->CloneScope() == StructuredCloneHolder::StructuredCloneScope::SameProcessSameThread ||
+             aHolder->CloneScope() == StructuredCloneHolder::StructuredCloneScope::SameProcessDifferentThread);
+
+  // We store the position of the wasmModule in the array as index.
+  if (JS_WriteUint32Pair(aWriter, SCTAG_DOM_WASM,
+                         aHolder->WasmModules().Length())) {
+    aHolder->WasmModules().AppendElement(aWasmModule);
+    return true;
+  }
+
+  return false;
+}
+
 } // anonymous namespace
 
 JSObject*
@@ -1033,7 +1068,11 @@ StructuredCloneHolder::CustomReadHandler(JSContext* aCx,
     // aIndex is the index of the cloned image.
     return ImageBitmap::ReadStructuredClone(aCx, aReader,
                                             parent, GetSurfaces(), aIndex);
-   }
+  }
+
+  if (aTag == SCTAG_DOM_WASM) {
+    return ReadWasmModule(aCx, aIndex, this);
+  }
 
   return ReadFullySerializableObjects(aCx, aReader, aTag);
 }
@@ -1095,6 +1134,16 @@ StructuredCloneHolder::CustomWriteHandler(JSContext* aCx,
     }
   }
 
+  // See if this is a WasmModule.
+  if ((mStructuredCloneScope == StructuredCloneScope::SameProcessSameThread ||
+       mStructuredCloneScope == StructuredCloneScope::SameProcessDifferentThread) &&
+      JS::IsWasmModuleObject(aObj)) {
+    RefPtr<JS::WasmModule> module = JS::GetWasmModule(aObj);
+    MOZ_ASSERT(module);
+
+    return WriteWasmModule(aWriter, module, this);
+  }
+
   return WriteFullySerializableObjects(aCx, aWriter, aObj);
 }
 
diff --git a/dom/base/StructuredCloneHolder.h b/dom/base/StructuredCloneHolder.h
index 2fbb608c7cb9..e6953d0f36f8 100644
--- a/dom/base/StructuredCloneHolder.h
+++ b/dom/base/StructuredCloneHolder.h
@@ -6,6 +6,7 @@
 #ifndef mozilla_dom_StructuredCloneHolder_h
 #define mozilla_dom_StructuredCloneHolder_h
 
+#include "jsapi.h"
 #include "js/StructuredClone.h"
 #include "mozilla/Move.h"
 #include "mozilla/UniquePtr.h"
@@ -178,6 +179,7 @@ public:
   bool HasClonedDOMObjects() const
   {
     return !mBlobImplArray.IsEmpty() ||
+           !mWasmModuleArray.IsEmpty() ||
            !mClonedSurfaces.IsEmpty();
   }
 
@@ -187,6 +189,12 @@ public:
     return mBlobImplArray;
   }
 
+  nsTArray<RefPtr<JS::WasmModule>>& WasmModules()
+  {
+    MOZ_ASSERT(mSupportsCloning, "WasmModules cannot be taken/set if cloning is not supported.");
+    return mWasmModuleArray;
+  }
+
   StructuredCloneScope CloneScope() const
   {
     return mStructuredCloneScope;
@@ -292,6 +300,9 @@ protected:
   // Used for cloning blobs in the structured cloning algorithm.
   nsTArray<RefPtr<BlobImpl>> mBlobImplArray;
 
+  // Used for cloning JS::WasmModules in the structured cloning algorithm.
+  nsTArray<RefPtr<JS::WasmModule>> mWasmModuleArray;
+
   // This is used for sharing the backend of ImageBitmaps.
   // The DataSourceSurface object must be thread-safely reference-counted.
   // The DataSourceSurface object will not be written ever via any ImageBitmap
diff --git a/dom/base/test/test_postMessages.html b/dom/base/test/test_postMessages.html
index 7ccfc244416f..a322f20b2019 100644
--- a/dom/base/test/test_postMessages.html
+++ b/dom/base/test/test_postMessages.html
@@ -11,13 +11,17 @@
 <script type="application/javascript;version=1.7">
 
 function setup_tests() {
-  SpecialPowers.pushPrefEnv({"set": [["dom.input.dirpicker", true]]}, next);
+  SpecialPowers.pushPrefEnv({"set": [["dom.input.dirpicker", true],
+                                     ["javascript.options.wasm", true]]}, next);
 }
 
 function getType(a) {
   if (a === null || a === undefined)
     return 'null';
 
+  if (a instanceof WebAssembly.Module)
+    return "wasm";
+
   if (Array.isArray(a))
     return 'array';
 
@@ -59,21 +63,32 @@ function compare(a, b) {
     return;
   }
 
+  if (type == 'wasm') {
+    var wasmA = new WebAssembly.Instance(a);
+    ok(wasmA instanceof WebAssembly.Instance, "got an instance");
+
+    var wasmB = new WebAssembly.Instance(b);
+    ok(wasmB instanceof WebAssembly.Instance, "got an instance");
+
+    ok(wasmA.exports.foo() === wasmB.exports.foo(), "Same result!");
+    ok(wasmB.exports.foo() === 42, "We want 42");
+  }
+
   if (type != 'null') {
     is (a.toSource(), b.toSource(), 'Matching using toSource()');
   }
 }
 
 var clonableObjects = [
-  'hello world',
-  123,
-  null,
-  true,
-  new Date(),
-  [ 1, 'test', true, new Date() ],
-  { a: true, b:  null, c: new Date(), d: [ true, false, {} ] },
-  new Blob([123], { type: 'plain/text' }),
-  new ImageData(2, 2),
+  { target: 'all', data: 'hello world' },
+  { target: 'all', data: 123 },
+  { target: 'all', data: null },
+  { target: 'all', data: true },
+  { target: 'all', data: new Date() },
+  { target: 'all', data: [ 1, 'test', true, new Date() ] },
+  { target: 'all', data: { a: true, b:  null, c: new Date(), d: [ true, false, {} ] } },
+  { target: 'all', data: new Blob([123], { type: 'plain/text' }) },
+  { target: 'all', data: new ImageData(2, 2) },
 ];
 
 function create_fileList() {
@@ -88,7 +103,7 @@ function create_fileList() {
     var domFile = fileList.files[0];
     is(domFile.name, "prefs.js", "fileName should be prefs.js");
 
-    clonableObjects.push(fileList.files);
+    clonableObjects.push({ target: 'all', data: fileList.files });
     script.destroy();
     next();
   }
@@ -115,7 +130,7 @@ function create_directory() {
       is(list.length, 1, "This list has 1 element");
       ok(list[0] instanceof Directory, "We have a directory.");
 
-      clonableObjects.push(list[0]);
+      clonableObjects.push({ target: 'all', data: list[0] });
       script.destroy();
       next();
     });
@@ -125,14 +140,41 @@ function create_directory() {
   script.sendAsyncMessage("dir.open");
 }
 
-function runTests(obj) {
-  ok(('clonableObjects' in obj) &&
-     ('transferableObjects' in obj) &&
-     (obj.clonableObjects || obj.transferableObjects), "We must run some test!");
+function create_wasmModule() {
+  info("Checking if we can play with WebAssembly...");
 
-  // cloning tests
+  if (!SpecialPowers.Cu.getJSTestingFunctions().wasmIsSupported()) {
+    next();
+    return;
+  }
+
+  ok(WebAssembly, "WebAssembly object should exist");
+  ok(WebAssembly.compile, "WebAssembly.compile function should exist");
+
+  const wasmTextToBinary = SpecialPowers.unwrap(SpecialPowers.Cu.getJSTestingFunctions().wasmTextToBinary);
+  const fooModuleCode = wasmTextToBinary(`(module
+    (func $foo (result i32) (i32.const 42))
+    (export "foo" $foo)
+  )`, 'new-format');
+
+  WebAssembly.compile(fooModuleCode).then((m) => {
+    ok(m instanceof WebAssembly.Module, "The WasmModule has been compiled.");
+    clonableObjects.push({ target: 'sameProcess', data: m });
+    next();
+  }, () => {
+    ok(false, "The compilation of the wasmModule failed.");
+  });
+}
+
+function runTests(obj) {
+  ok(('clonableObjectsEveryWhere' in obj) &&
+     ('clonableObjectsSameProcess' in obj) &&
+     ('transferableObjects' in obj) &&
+     (obj.clonableObjectsEveryWhere || obj.clonableObjectsSameProcess || obj.transferableObjects), "We must run some test!");
+
+  // cloning tests - everyWhere
   new Promise(function(resolve, reject) {
-    if (!obj.clonableObjects) {
+    if (!obj.clonableObjectsEveryWhere) {
       resolve();
       return;
     }
@@ -146,8 +188,13 @@ function runTests(obj) {
 
       var object = clonableObjects[clonableObjectsId++];
 
-      obj.send(object, []).then(function(received) {
-        compare(received.data, object);
+      if (object.target != 'all') {
+        runClonableTest();
+        return;
+      }
+
+      obj.send(object.data, []).then(function(received) {
+        compare(received.data, object.data);
         runClonableTest();
       });
     }
@@ -155,6 +202,38 @@ function runTests(obj) {
     runClonableTest();
   })
 
+  // clonable same process
+  .then(function() {
+    return new Promise(function(resolve, reject) {
+      if (!obj.clonableObjectsSameProcess) {
+        resolve();
+        return;
+      }
+
+      var clonableObjectsId = 0;
+      function runClonableTest() {
+        if (clonableObjectsId >= clonableObjects.length) {
+          resolve();
+          return;
+        }
+
+        var object = clonableObjects[clonableObjectsId++];
+
+        if (object.target != 'sameProcess') {
+          runClonableTest();
+          return;
+        }
+
+        obj.send(object.data, []).then(function(received) {
+          compare(received.data, object.data);
+          runClonableTest();
+        });
+      }
+
+      runClonableTest();
+    });
+  })
+
   // transfering tests
   .then(function() {
     if (!obj.transferableObjects) {
@@ -234,7 +313,8 @@ function test_windowToWindow() {
   }
 
   runTests({
-    clonableObjects: true,
+    clonableObjectsEveryWhere: true,
+    clonableObjectsSameProcess: true,
     transferableObjects: true,
     send: function(what, ports) {
       return new Promise(function(r, rr) {
@@ -287,7 +367,8 @@ function test_windowToIframeURL(url) {
   ifr.src = url;
   ifr.onload = function() {
     runTests({
-      clonableObjects: true,
+      clonableObjectsEveryWhere: true,
+      clonableObjectsSameProcess: false,
       transferableObjects: true,
       send: function(what, ports) {
         return new Promise(function(r, rr) {
@@ -334,7 +415,8 @@ function test_workers() {
     }
 
     runTests({
-      clonableObjects: true,
+      clonableObjectsEveryWhere: true,
+      clonableObjectsSameProcess: true,
       transferableObjects: true,
       send: function(what, ports) {
         return new Promise(function(r, rr) {
@@ -377,7 +459,8 @@ function test_broadcastChannel() {
   }
 
   runTests({
-    clonableObjects: true,
+    clonableObjectsEveryWhere: true,
+    clonableObjectsSameProcess: false,
     transferableObjects: false,
     send: function(what, ports) {
       return new Promise(function(r, rr) {
@@ -422,7 +505,8 @@ function test_broadcastChannel_inWorkers() {
     }
 
     runTests({
-      clonableObjects: true,
+      clonableObjectsEveryWhere: true,
+      clonableObjectsSameProcess: false,
       transferableObjects: false,
       send: function(what, ports) {
         return new Promise(function(r, rr) {
@@ -463,7 +547,8 @@ function test_messagePort() {
   }
 
   runTests({
-    clonableObjects: true,
+    clonableObjectsEveryWhere: true,
+    clonableObjectsSameProcess: false,
     transferableObjects: true,
     send: function(what, ports) {
       return new Promise(function(r, rr) {
@@ -508,7 +593,8 @@ function test_messagePort_inWorkers() {
     }
 
     runTests({
-      clonableObjects: true,
+      clonableObjectsEveryWhere: true,
+      clonableObjectsSameProcess: false,
       transferableObjects: true,
       send: function(what, ports) {
         return new Promise(function(r, rr) {
@@ -535,6 +621,7 @@ var tests = [
 
   create_fileList,
   create_directory,
+  create_wasmModule,
 
   test_windowToWindow,
   test_windowToIframe,
diff --git a/dom/ipc/StructuredCloneData.cpp b/dom/ipc/StructuredCloneData.cpp
index 9d86d96ae6db..98f56904fa83 100644
--- a/dom/ipc/StructuredCloneData.cpp
+++ b/dom/ipc/StructuredCloneData.cpp
@@ -46,6 +46,7 @@ StructuredCloneData::Copy(const StructuredCloneData& aData)
   BlobImpls().AppendElements(aData.BlobImpls());
 
   MOZ_ASSERT(GetSurfaces().IsEmpty());
+  MOZ_ASSERT(WasmModules().IsEmpty());
 
   mInitialized = true;