diff --git a/contrib/fuzz/manifest.cc b/contrib/fuzz/manifest.cc
--- a/contrib/fuzz/manifest.cc
+++ b/contrib/fuzz/manifest.cc
@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 
+#include "FuzzedDataProvider.h"
 #include "pyutil.h"
 
 #include <string>
@@ -24,7 +25,7 @@
       lm[e]
       e in lm
       (e + 'nope') in lm
-  lm[b'xyzzy'] = (b'\0' * 20, 'x')
+  lm[b'xyzzy'] = (b'\0' * nlen, 'x')
   # do an insert, text should change
   assert lm.text() != mdata, "insert should change text and didn't: %r %r" % (lm.text(), mdata)
   cloned = lm.filtercopy(lambda x: x != 'xyzzy')
@@ -51,10 +52,14 @@
 	if (Size > 100000) {
 		return 0;
 	}
+	FuzzedDataProvider provider(Data, Size);
+	Py_ssize_t nodelength = provider.ConsumeBool() ? 20 : 32;
+	PyObject *nlen = PyLong_FromSsize_t(nodelength);
 	PyObject *mtext =
 	    PyBytes_FromStringAndSize((const char *)Data, (Py_ssize_t)Size);
 	PyObject *locals = PyDict_New();
 	PyDict_SetItemString(locals, "mdata", mtext);
+	PyDict_SetItemString(locals, "nlen", nlen);
 	PyObject *res = PyEval_EvalCode(code, contrib::pyglobals(), locals);
 	if (!res) {
 		PyErr_Print();
diff --git a/contrib/fuzz/manifest_corpus.py b/contrib/fuzz/manifest_corpus.py
--- a/contrib/fuzz/manifest_corpus.py
+++ b/contrib/fuzz/manifest_corpus.py
@@ -10,7 +10,7 @@
 with zipfile.ZipFile(args.out[0], "w", zipfile.ZIP_STORED) as zf:
     zf.writestr(
         "manifest_zero",
-        '''PKG-INFO\09b3ed8f2b81095a13064402e930565f083346e9a
+        '''\0PKG-INFO\09b3ed8f2b81095a13064402e930565f083346e9a
 README\080b6e76643dcb44d4bc729e932fc464b3e36dbe3
 hg\0b6444347c629cc058d478023905cfb83b7f5bb9d
 mercurial/__init__.py\0b80de5d138758541c5f05265ad144ab9fa86d1db
@@ -25,9 +25,14 @@
 tkmerge\03c922edb43a9c143682f7bc7b00f98b3c756ebe7
 ''',
     )
-    zf.writestr("badmanifest_shorthashes", "narf\0aa\nnarf2\0aaa\n")
+    zf.writestr("badmanifest_shorthashes", "\0narf\0aa\nnarf2\0aaa\n")
     zf.writestr(
         "badmanifest_nonull",
-        "narf\0cccccccccccccccccccccccccccccccccccccccc\n"
+        "\0narf\0cccccccccccccccccccccccccccccccccccccccc\n"
         "narf2aaaaaaaaaaaaaaaaaaaa\n",
     )
+
+    zf.writestr(
+        "manifest_long_nodes",
+        "\1a\0ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff\n",
+    )