diff --git a/src/hb-ot-layout-gpos-table.hh b/src/hb-ot-layout-gpos-table.hh
index 0e389b761..e4189754f 100644
--- a/src/hb-ot-layout-gpos-table.hh
+++ b/src/hb-ot-layout-gpos-table.hh
@@ -492,9 +492,13 @@ struct Anchor
   {
     TRACE_SUBSET (this);
     if (c->plan->drop_hints)
+    {
       // AnchorFormat 2 and 3 just containing extra hinting information, so
       // if hints are being dropped convert to format 1.
+      if (u.format != 1 && u.format != 2 && u.format != 3)
+        return_trace (false);
       return_trace (bool (reinterpret_cast<Anchor *> (u.format1.copy (c->serializer))));
+    }
 
     switch (u.format) {
     case 1: return_trace (bool (reinterpret_cast<Anchor *> (u.format1.copy (c->serializer))));
diff --git a/test/fuzzing/fonts/clusterfuzz-testcase-minimized-hb-subset-fuzzer-5858518134554624 b/test/fuzzing/fonts/clusterfuzz-testcase-minimized-hb-subset-fuzzer-5858518134554624
new file mode 100644
index 000000000..90a743b9f
Binary files /dev/null and b/test/fuzzing/fonts/clusterfuzz-testcase-minimized-hb-subset-fuzzer-5858518134554624 differ