diff --git a/tools/gen-postmortem-metadata.py b/tools/gen-postmortem-metadata.py
index 188de931c89d..f0e3c7492ec6 100644
--- a/tools/gen-postmortem-metadata.py
+++ b/tools/gen-postmortem-metadata.py
@@ -72,6 +72,7 @@
     { 'name': 'ConsStringTag',          'value': 'kConsStringTag' },
     { 'name': 'ExternalStringTag',      'value': 'kExternalStringTag' },
     { 'name': 'SlicedStringTag',        'value': 'kSlicedStringTag' },
+    { 'name': 'ThinStringTag',          'value': 'kThinStringTag' },
 
     { 'name': 'HeapObjectTag',          'value': 'kHeapObjectTag' },
     { 'name': 'HeapObjectTagMask',      'value': 'kHeapObjectTagMask' },