The check for internalized strings relied on the fact that we had less

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 2e2a01845b7661696bc4fb841701891526d5d4eb..2557cbe332cc271f9f8790f96cdafd51f4f5b6da 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -575,8 +575,7 @@ const uint32_t kStringTag = 0x0;
 const uint32_t kNotStringTag = 0x80;
 
 // Bit 6 indicates that the object is an internalized string (if set) or not.
-// There are not enough types that the non-string types (with bit 7 set) can
-// have bit 6 set too.
+// Bit 7 has to be clear as well.
 const uint32_t kIsInternalizedMask = 0x40;
 const uint32_t kNotInternalizedTag = 0x0;
 const uint32_t kInternalizedTag = 0x40;