diff --git a/src/3rdparty/v8/src/api.cc b/src/3rdparty/v8/src/api.cc
index 1becc61..70d0a8a 100644
--- a/src/3rdparty/v8/src/api.cc
+++ b/src/3rdparty/v8/src/api.cc
@@ -3911,7 +3911,7 @@ String::CompleteHashData String::CompleteHash() const {
   CompleteHashData result;
   result.length = str->length();
   result.hash = str->Hash();
-  if (str->IsSeqString())
+  if (str->IsSeqAsciiString() && str->IsSymbol())
       result.symbol_id = i::SeqString::cast(*str)->symbol_id();
   return result;
 }
diff --git a/src/3rdparty/v8/src/heap-inl.h b/src/3rdparty/v8/src/heap-inl.h
index 3e036b6..d1f66a8 100644
--- a/src/3rdparty/v8/src/heap-inl.h
+++ b/src/3rdparty/v8/src/heap-inl.h
@@ -127,7 +127,6 @@ MaybeObject* Heap::AllocateAsciiSymbol(Vector<const char> str,
   String* answer = String::cast(result);
   answer->set_length(str.length());
   answer->set_hash_field(hash_field);
-  SeqString::cast(answer)->set_symbol_id(0);
 
   ASSERT_EQ(size, answer->Size());
 
@@ -161,7 +160,6 @@ MaybeObject* Heap::AllocateTwoByteSymbol(Vector<const uc16> str,
   String* answer = String::cast(result);
   answer->set_length(str.length());
   answer->set_hash_field(hash_field);
-  SeqString::cast(answer)->set_symbol_id(0);
 
   ASSERT_EQ(size, answer->Size());
 
diff --git a/src/3rdparty/v8/src/heap.cc b/src/3rdparty/v8/src/heap.cc
index 933cec6..f678517 100644
--- a/src/3rdparty/v8/src/heap.cc
+++ b/src/3rdparty/v8/src/heap.cc
@@ -4490,7 +4490,6 @@ MaybeObject* Heap::AllocateRawAsciiString(int length, PretenureFlag pretenure) {
   HeapObject::cast(result)->set_map_no_write_barrier(ascii_string_map());
   String::cast(result)->set_length(length);
   String::cast(result)->set_hash_field(String::kEmptyHashField);
-  SeqString::cast(result)->set_symbol_id(0);
   ASSERT_EQ(size, HeapObject::cast(result)->Size());
   return result;
 }
@@ -4527,7 +4526,6 @@ MaybeObject* Heap::AllocateRawTwoByteString(int length,
   HeapObject::cast(result)->set_map_no_write_barrier(string_map());
   String::cast(result)->set_length(length);
   String::cast(result)->set_hash_field(String::kEmptyHashField);
-  SeqString::cast(result)->set_symbol_id(0);
   ASSERT_EQ(size, HeapObject::cast(result)->Size());
   return result;
 }