diff --git a/deps/v8/include/v8-version.h b/deps/v8/include/v8-version.h
index dafa83627b224a..8c4bc0237702ed 100644
--- a/deps/v8/include/v8-version.h
+++ b/deps/v8/include/v8-version.h
@@ -11,7 +11,7 @@
 #define V8_MAJOR_VERSION 6
 #define V8_MINOR_VERSION 4
 #define V8_BUILD_NUMBER 388
-#define V8_PATCH_LEVEL 41
+#define V8_PATCH_LEVEL 42
 
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)
diff --git a/deps/v8/src/frames.cc b/deps/v8/src/frames.cc
index bd1abda4de8650..23713197f59d66 100644
--- a/deps/v8/src/frames.cc
+++ b/deps/v8/src/frames.cc
@@ -1013,6 +1013,15 @@ JSFunction* JavaScriptFrame::function() const {
   return JSFunction::cast(function_slot_object());
 }
 
+Object* JavaScriptFrame::unchecked_function() const {
+  // During deoptimization of an optimized function, we may have yet to
+  // materialize some closures on the stack. The arguments marker object
+  // marks this case.
+  DCHECK(function_slot_object()->IsJSFunction() ||
+         isolate()->heap()->arguments_marker() == function_slot_object());
+  return function_slot_object();
+}
+
 Object* JavaScriptFrame::receiver() const { return GetParameter(-1); }
 
 Object* JavaScriptFrame::context() const {
diff --git a/deps/v8/src/frames.h b/deps/v8/src/frames.h
index a72832af06dbc0..e21d62764b30c3 100644
--- a/deps/v8/src/frames.h
+++ b/deps/v8/src/frames.h
@@ -684,6 +684,7 @@ class JavaScriptFrame : public StandardFrame {
 
   // Accessors.
   virtual JSFunction* function() const;
+  Object* unchecked_function() const;
   Object* receiver() const override;
   Object* context() const override;
   Script* script() const override;
diff --git a/deps/v8/src/profiler/sampling-heap-profiler.cc b/deps/v8/src/profiler/sampling-heap-profiler.cc
index 0aa0525633ca2c..51fe8866fa1c19 100644
--- a/deps/v8/src/profiler/sampling-heap-profiler.cc
+++ b/deps/v8/src/profiler/sampling-heap-profiler.cc
@@ -157,12 +157,21 @@ SamplingHeapProfiler::AllocationNode* SamplingHeapProfiler::AddStack() {
   std::vector<SharedFunctionInfo*> stack;
   JavaScriptFrameIterator it(isolate_);
   int frames_captured = 0;
+  bool found_arguments_marker_frames = false;
   while (!it.done() && frames_captured < stack_depth_) {
     JavaScriptFrame* frame = it.frame();
-    SharedFunctionInfo* shared = frame->function()->shared();
-    stack.push_back(shared);
-
-    frames_captured++;
+    // If we are materializing objects during deoptimization, inlined
+    // closures may not yet be materialized, and this includes the
+    // closure on the stack. Skip over any such frames (they'll be
+    // in the top frames of the stack). The allocations made in this
+    // sensitive moment belong to the formerly optimized frame anyway.
+    if (frame->unchecked_function()->IsJSFunction()) {
+      SharedFunctionInfo* shared = frame->function()->shared();
+      stack.push_back(shared);
+      frames_captured++;
+    } else {
+      found_arguments_marker_frames = true;
+    }
     it.Advance();
   }
 
@@ -209,6 +218,12 @@ SamplingHeapProfiler::AllocationNode* SamplingHeapProfiler::AddStack() {
     }
     node = node->FindOrAddChildNode(name, script_id, shared->start_position());
   }
+
+  if (found_arguments_marker_frames) {
+    node =
+        node->FindOrAddChildNode("(deopt)", v8::UnboundScript::kNoScriptId, 0);
+  }
+
   return node;
 }
 
diff --git a/deps/v8/test/cctest/test-heap-profiler.cc b/deps/v8/test/cctest/test-heap-profiler.cc
index ce015777e5d6e9..a0796ccd56c158 100644
--- a/deps/v8/test/cctest/test-heap-profiler.cc
+++ b/deps/v8/test/cctest/test-heap-profiler.cc
@@ -3083,7 +3083,7 @@ TEST(SamplingHeapProfilerPretenuredInlineAllocations) {
   // Suppress randomness to avoid flakiness in tests.
   v8::internal::FLAG_sampling_heap_profiler_suppress_randomness = true;
 
-  // Grow new space unitl maximum capacity reached.
+  // Grow new space until maximum capacity reached.
   while (!CcTest::heap()->new_space()->IsAtMaximumCapacity()) {
     CcTest::heap()->new_space()->Grow();
   }
@@ -3138,3 +3138,49 @@ TEST(SamplingHeapProfilerPretenuredInlineAllocations) {
 
   CHECK_GE(count, 8000);
 }
+
+TEST(SamplingHeapProfilerSampleDuringDeopt) {
+  i::FLAG_allow_natives_syntax = true;
+
+  v8::HandleScope scope(v8::Isolate::GetCurrent());
+  LocalContext env;
+  v8::HeapProfiler* heap_profiler = env->GetIsolate()->GetHeapProfiler();
+
+  // Suppress randomness to avoid flakiness in tests.
+  v8::internal::FLAG_sampling_heap_profiler_suppress_randomness = true;
+
+  // Small sample interval to force each object to be sampled.
+  heap_profiler->StartSamplingHeapProfiler(i::kPointerSize);
+
+  // Lazy deopt from runtime call from inlined callback function.
+  const char* source =
+      "var b = "
+      "  [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25];"
+      "(function f() {"
+      "  var result = 0;"
+      "  var lazyDeopt = function(deopt) {"
+      "    var callback = function(v,i,o) {"
+      "      result += i;"
+      "      if (i == 13 && deopt) {"
+      "          %DeoptimizeNow();"
+      "      }"
+      "      return v;"
+      "    };"
+      "    b.map(callback);"
+      "  };"
+      "  lazyDeopt();"
+      "  lazyDeopt();"
+      "  %OptimizeFunctionOnNextCall(lazyDeopt);"
+      "  lazyDeopt();"
+      "  lazyDeopt(true);"
+      "  lazyDeopt();"
+      "})();";
+
+  CompileRun(source);
+  // Should not crash.
+
+  std::unique_ptr<v8::AllocationProfile> profile(
+      heap_profiler->GetAllocationProfile());
+  CHECK(profile);
+  heap_profiler->StopSamplingHeapProfiler();
+}