diff --git a/elpy/json_encoder.py b/elpy/json_encoder.py
new file mode 100644
index 000000000..43e7d2050
--- /dev/null
+++ b/elpy/json_encoder.py
@@ -0,0 +1,10 @@
+import json
+import pathlib
+
+
+class JSONEncoder(json.JSONEncoder):
+    def default(self, o):
+        if isinstance(o, pathlib.Path):
+            return str(o)
+        else:
+            return super().default(o)
diff --git a/elpy/rpc.py b/elpy/rpc.py
index 07b2ce97e..33c098e07 100644
--- a/elpy/rpc.py
+++ b/elpy/rpc.py
@@ -10,6 +10,7 @@
 import json
 import sys
 import traceback
+from .json_encoder import JSONEncoder
 
 
 class JSONRPCServer(object):
@@ -74,7 +75,8 @@ def write_json(self, **kwargs):
         It's not possible with this method to write non-objects.
 
         """
-        self.stdout.write(json.dumps(kwargs) + "\n")
+        serialized_value = JSONEncoder().encode(kwargs)
+        self.stdout.write(serialized_value + "\n")
         self.stdout.flush()
 
     def handle_request(self):
diff --git a/elpy/tests/support.py b/elpy/tests/support.py
index 1e79654f3..9d7de6b37 100644
--- a/elpy/tests/support.py
+++ b/elpy/tests/support.py
@@ -13,15 +13,16 @@
 """
 
 import os
+import pathlib
+import re
 import shutil
 import sys
 import tempfile
 import unittest
-import re
 
-from elpy.tests import compat
-from elpy.rpc import Fault
 from elpy import jedibackend
+from elpy.rpc import Fault
+from elpy.tests import compat
 
 
 class BackendTestCase(unittest.TestCase):
@@ -55,7 +56,7 @@ def project_file(self, relname, contents):
             fobj = open(full_name, "w")
         with fobj as f:
             f.write(contents)
-        return full_name
+        return pathlib.Path(full_name)
 
 
 class GenericRPCTests(object):
diff --git a/requirements-rpc.txt b/requirements-rpc.txt
index 40e78f53c..56ba103da 100644
--- a/requirements-rpc.txt
+++ b/requirements-rpc.txt
@@ -1,4 +1,4 @@
-jedi==0.17.2
+jedi==0.18.0
 rope==0.17.0
 autopep8==1.5.4
 yapf==0.30