diff --git a/common.gypi b/common.gypi
index a58d48b0c5eb9a..7428367750fac2 100644
--- a/common.gypi
+++ b/common.gypi
@@ -36,7 +36,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.29',
+    'v8_embedder_string': '-node.30',
 
     ##### V8 defaults for Node.js #####
 
diff --git a/deps/v8/src/runtime/runtime-test.cc b/deps/v8/src/runtime/runtime-test.cc
index fcaada5711d487..7dcc05ab485408 100644
--- a/deps/v8/src/runtime/runtime-test.cc
+++ b/deps/v8/src/runtime/runtime-test.cc
@@ -27,6 +27,7 @@
 #include "src/logging/counters.h"
 #include "src/objects/heap-object-inl.h"
 #include "src/objects/js-array-inl.h"
+#include "src/objects/js-collection-inl.h"
 #include "src/objects/js-function-inl.h"
 #include "src/objects/js-regexp-inl.h"
 #include "src/objects/managed-inl.h"
@@ -1730,5 +1731,14 @@ RUNTIME_FUNCTION(Runtime_SharedGC) {
   return ReadOnlyRoots(isolate).undefined_value();
 }
 
+RUNTIME_FUNCTION(Runtime_GetWeakCollectionSize) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  Handle<JSWeakCollection> collection = args.at<JSWeakCollection>(0);
+
+  return Smi::FromInt(
+      EphemeronHashTable::cast(collection->table()).NumberOfElements());
+}
+
 }  // namespace internal
 }  // namespace v8
diff --git a/deps/v8/src/runtime/runtime.h b/deps/v8/src/runtime/runtime.h
index 877b277a5e26cb..d0f81cf2f7672a 100644
--- a/deps/v8/src/runtime/runtime.h
+++ b/deps/v8/src/runtime/runtime.h
@@ -498,6 +498,7 @@ namespace internal {
   F(GetInitializerFunction, 1, 1)             \
   F(GetOptimizationStatus, 1, 1)              \
   F(GetUndetectable, 0, 1)                    \
+  F(GetWeakCollectionSize, 1, 1)              \
   F(GlobalPrint, 1, 1)                        \
   F(HasDictionaryElements, 1, 1)              \
   F(HasDoubleElements, 1, 1)                  \
diff --git a/deps/v8/test/mjsunit/harmony/symbol-as-weakmap-key.js b/deps/v8/test/mjsunit/harmony/symbol-as-weakmap-key.js
index 0e97ea1accca58..f644fccb00022d 100644
--- a/deps/v8/test/mjsunit/harmony/symbol-as-weakmap-key.js
+++ b/deps/v8/test/mjsunit/harmony/symbol-as-weakmap-key.js
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-symbol-as-weakmap-key --expose-gc
+// Flags: --harmony-symbol-as-weakmap-key --expose-gc --allow-natives-syntax --noincremental-marking
 
 (function TestWeakMapWithNonRegisteredSymbolKey() {
   const key = Symbol('123');
@@ -28,16 +28,17 @@
   const outerKey = Symbol('234');
   const outerValue = 1;
   map.set(outerKey, outerValue);
-  {
+  (function () {
     const innerKey = Symbol('123');
     const innerValue = 1;
     map.set(innerKey, innerValue);
     assertTrue(map.has(innerKey));
     assertSame(innerValue, map.get(innerKey));
-  }
+  })();
   gc();
   assertTrue(map.has(outerKey));
   assertSame(outerValue, map.get(outerKey));
+  assertEquals(1, %GetWeakCollectionSize(map));
 })();
 
 (function TestWeakMapWithRegisteredSymbolKey() {
@@ -74,13 +75,14 @@
   const set = new WeakSet();
   const outerKey = Symbol('234');
   set.add(outerKey);
-  {
+  (function () {
     const innerKey = Symbol('123');
     set.add(innerKey);
     assertTrue(set.has(innerKey));
-  }
-  gc();
+  })();
   assertTrue(set.has(outerKey));
+  gc();
+  assertEquals(1, %GetWeakCollectionSize(set));
 })();
 
 (function TestWeakSetWithRegisteredSymbolKey() {