diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index d3f9b1a8..654c0657 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: ['2.7', '3.5', '3.6', '3.7', '3.8', '3.9', 'pypy3']
+        python-version: ['3.5', '3.6', '3.7', '3.8', '3.9', '3.10', '3.11', 'pypy3']
 
     steps:
     - uses: actions/checkout@v2
diff --git a/dpkt/ntp.py b/dpkt/ntp.py
index 548081b4..b82a4a26 100644
--- a/dpkt/ntp.py
+++ b/dpkt/ntp.py
@@ -39,8 +39,8 @@ class NTP(dpkt.Packet):
     __hdr__ = (
         ('flags', 'B', 0),
         ('stratum', 'B', 0),
-        ('interval', 'B', 0),
-        ('precision', 'B', 0),
+        ('interval', 'b', 0),
+        ('precision', 'b', 0),
         ('delay', 'I', 0),
         ('dispersion', 'I', 0),
         ('id', '4s', 0),