diff --git a/contrib/fuzz/Makefile b/contrib/fuzz/Makefile
--- a/contrib/fuzz/Makefile
+++ b/contrib/fuzz/Makefile
@@ -135,12 +135,23 @@ revlog_fuzzer: sanpy revlog.cc manifest.
 revlog_corpus.zip:
 	python revlog_corpus.py $$OUT/revlog_fuzzer_seed_corpus.zip
 
+dirstate_fuzzer: sanpy dirstate.cc manifest.o charencode.o parsers.o dirs.o pathencode.o revlog.o pyutil.o
+	$(CXX) $(CXXFLAGS) `$$OUT/sanpy/bin/python-config --cflags` \
+	  -Wno-register -Wno-macro-redefined \
+	  -I../../mercurial dirstate.cc \
+	  manifest.o charencode.o parsers.o dirs.o pathencode.o revlog.o pyutil.o \
+	  -lFuzzingEngine `$$OUT/sanpy/bin/python-config --ldflags` \
+	  -o $$OUT/dirstate_fuzzer
+
+dirstate_corpus.zip:
+	python dirstate_corpus.py $$OUT/dirstate_fuzzer_seed_corpus.zip
+
 clean:
 	$(RM) *.o *_fuzzer \
 	  bdiff \
 	  mpatch \
 	  xdiff
 
-oss-fuzz: bdiff_fuzzer mpatch_fuzzer mpatch_corpus.zip xdiff_fuzzer manifest_fuzzer manifest_corpus.zip revlog_fuzzer revlog_corpus.zip
+oss-fuzz: bdiff_fuzzer mpatch_fuzzer mpatch_corpus.zip xdiff_fuzzer manifest_fuzzer manifest_corpus.zip revlog_fuzzer revlog_corpus.zip dirstate_fuzzer dirstate_corpus.zip
 
 .PHONY: all clean oss-fuzz sanpy
diff --git a/contrib/fuzz/dirstate.cc b/contrib/fuzz/dirstate.cc
new file mode 100644
--- /dev/null
+++ b/contrib/fuzz/dirstate.cc
@@ -0,0 +1,48 @@
+#include <Python.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <string>
+
+#include "pyutil.h"
+
+extern "C" {
+
+static PyCodeObject *code;
+
+extern "C" int LLVMFuzzerInitialize(int *argc, char ***argv)
+{
+	contrib::initpy(*argv[0]);
+	code = (PyCodeObject *)Py_CompileString(R"py(
+from parsers import parse_dirstate
+try:
+    dmap = {}
+    copymap = {}
+    p = parse_dirstate(dmap, copymap, data)
+except Exception as e:
+    pass
+    # uncomment this print if you're editing this Python code
+    # to debug failures.
+    # print e
+)py",
+	                                        "fuzzer", Py_file_input);
+	return 0;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
+{
+	PyObject *text =
+	    PyBytes_FromStringAndSize((const char *)Data, (Py_ssize_t)Size);
+	PyObject *locals = PyDict_New();
+	PyDict_SetItemString(locals, "data", text);
+	PyObject *res = PyEval_EvalCode(code, contrib::pyglobals(), locals);
+	if (!res) {
+		PyErr_Print();
+	}
+	Py_XDECREF(res);
+	Py_DECREF(locals);
+	Py_DECREF(text);
+	return 0; // Non-zero return values are reserved for future use.
+}
+}
diff --git a/contrib/fuzz/dirstate_corpus.py b/contrib/fuzz/dirstate_corpus.py
new file mode 100644
--- /dev/null
+++ b/contrib/fuzz/dirstate_corpus.py
@@ -0,0 +1,18 @@
+from __future__ import absolute_import, print_function
+
+import argparse
+import os
+import zipfile
+
+ap = argparse.ArgumentParser()
+ap.add_argument("out", metavar="some.zip", type=str, nargs=1)
+args = ap.parse_args()
+
+reporoot = os.path.normpath(os.path.join(os.path.dirname(__file__),
+                                         '..', '..'))
+dirstate = os.path.join(reporoot, '.hg', 'dirstate')
+
+with zipfile.ZipFile(args.out[0], "w", zipfile.ZIP_STORED) as zf:
+    if os.path.exists(dirstate):
+        with open(dirstate) as f:
+            zf.writestr("dirstate", f.read())