diff --git a/.azure-pipelines/posix-steps.yml b/.azure-pipelines/posix-steps.yml
index 2a368089730..29b43e09344 100644
--- a/.azure-pipelines/posix-steps.yml
+++ b/.azure-pipelines/posix-steps.yml
@@ -66,7 +66,9 @@ steps:
         COMMAND: make
 
 - ${{ if eq(parameters.patchcheck, 'true') }}:
-  - script: ./python Tools/scripts/patchcheck.py --ci true
+  - script: |
+      git fetch origin
+      ./python Tools/scripts/patchcheck.py --ci true
     displayName: 'Run patchcheck.py'
     condition: and(succeeded(), eq(variables['Build.Reason'], 'PullRequest'))
 
diff --git a/Tools/scripts/patchcheck.py b/Tools/scripts/patchcheck.py
index 4cab66c8e97..a324eafc52b 100755
--- a/Tools/scripts/patchcheck.py
+++ b/Tools/scripts/patchcheck.py
@@ -130,6 +130,8 @@ def changed_files(base_branch=None):
         with subprocess.Popen(cmd.split(),
                               stdout=subprocess.PIPE,
                               cwd=SRCDIR) as st:
+            if st.wait() != 0:
+                sys.exit(f'error running {cmd}')
             for line in st.stdout:
                 line = line.decode().rstrip()
                 status_text, filename = line.split(maxsplit=1)