diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 3d0cc15..9cb0f6c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -9,7 +9,7 @@ jobs:
   test:
     strategy:
       matrix:
-        python: ['3.9', '3.10', '3.11', '3.12']
+        python: ['3.9', '3.10', '3.11', '3.12', '3.13']
         platform: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.platform }}
     steps:
diff --git a/noxfile.py b/noxfile.py
index d1c8d85..fa8177a 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -37,7 +37,7 @@ def build_and_check_dists(session):
     session.run("python", "-m", "twine", "check", "dist/*")
 
 
-@nox.session(python=["3.9", "3.10", "3.11", "3.12"])
+@nox.session(python=["3.9", "3.10", "3.11", "3.12", "3.13"])
 def tests(session):
     session.install("pytest")
     session.install("pytest-asyncio")
diff --git a/src/jsonata/functions.py b/src/jsonata/functions.py
index e392f12..9b2c849 100644
--- a/src/jsonata/functions.py
+++ b/src/jsonata/functions.py
@@ -722,7 +722,7 @@ def safe_replace_first(s: str, pattern: re.Pattern, replacement: str) -> Optiona
         r = None
         for i in range(0, 10):
             try:
-                r = re.sub(pattern, replacement, s, 1)
+                r = re.sub(pattern, replacement, s, count=1)
                 break
             except Exception as e:
                 msg = str(e)