diff --git a/src/hb-ot-layout-common.hh b/src/hb-ot-layout-common.hh
index fe49afbde..019370908 100644
--- a/src/hb-ot-layout-common.hh
+++ b/src/hb-ot-layout-common.hh
@@ -1651,7 +1651,7 @@ struct ClassDefFormat1
     unsigned glyph_count = glyph_max - glyph_min + 1;
 
     startGlyph = glyph_min;
-    classValue.serialize (c, glyph_count);
+    if (unlikely (!classValue.serialize (c, glyph_count))) return_trace (false);
     for (const hb_pair_t<hb_codepoint_t, unsigned>& gid_klass_pair : + it)
     {
       unsigned idx = gid_klass_pair.first - glyph_min;
diff --git a/test/fuzzing/fonts/clusterfuzz-testcase-minimized-hb-subset-fuzzer-5704307501694976 b/test/fuzzing/fonts/clusterfuzz-testcase-minimized-hb-subset-fuzzer-5704307501694976
new file mode 100644
index 000000000..f2f0ec9c9
Binary files /dev/null and b/test/fuzzing/fonts/clusterfuzz-testcase-minimized-hb-subset-fuzzer-5704307501694976 differ