diff --git a/tests/fakegithub.py b/tests/fakegithub.py
index f278e49401..ef0478f75f 100644
--- a/tests/fakegithub.py
+++ b/tests/fakegithub.py
@@ -283,6 +283,10 @@ class FakeIssue(object):
     def pull_request(self):
         return FakePull(self._fake_pull_request)
 
+    @property
+    def number(self):
+        return self._fake_pull_request.number
+
 
 class FakeFile(object):
     def __init__(self, filename):
@@ -449,6 +453,14 @@ class FakeGithubClient(object):
         def tokenize(s):
             return re.findall(r'[\w]+', s)
 
+        def query_is_sha(s):
+            return re.match(r'[a-z0-9]{40}', s)
+
+        if query_is_sha(query):
+            return (FakeIssueSearchResult(FakeIssue(pr))
+                    for pr in self._data.pull_requests.values()
+                    if pr.head_sha == query)
+
         parts = tokenize(query)
         terms = set()
         results = []
@@ -471,4 +483,4 @@ class FakeGithubClient(object):
                 issue = FakeIssue(pr)
                 results.append(FakeIssueSearchResult(issue))
 
-        return results
+        return iter(results)
diff --git a/zuul/driver/github/githubconnection.py b/zuul/driver/github/githubconnection.py
index 69a902c2e5..f201110620 100644
--- a/zuul/driver/github/githubconnection.py
+++ b/zuul/driver/github/githubconnection.py
@@ -1280,7 +1280,7 @@ class GithubConnection(BaseConnection):
 
     def getPull(self, project_name, number, event=None):
         log = get_annotated_logger(self.log, event)
-        github = self.getGithubClient(project_name)
+        github = self.getGithubClient(project_name, zuul_event_id=event)
         owner, proj = project_name.split('/')
         for retry in range(5):
             try:
@@ -1344,6 +1344,8 @@ class GithubConnection(BaseConnection):
 
     def getPullBySha(self, sha, project_name, event):
         log = get_annotated_logger(self.log, event)
+
+        # Serve from the cache if existing
         cached_pr_numbers = self._sha_pr_cache.get(project_name, sha)
         if len(cached_pr_numbers) > 1:
             raise Exception('Multiple pulls found with head sha %s' % sha)
@@ -1352,31 +1354,20 @@ class GithubConnection(BaseConnection):
                 pr_body, pr_obj = self.getPull(project_name, pr, event)
                 return pr_body
 
-        pulls = []
-        github = self.getGithubClient(project_name)
-        owner, repository = project_name.split('/')
-        repo = github.repository(owner, repository)
-        for pr in repo.pull_requests(state='open',
-                                     # We sort by updated from oldest to newest
-                                     # as that will prefer more recently
-                                     # PRs in our LRU cache.
-                                     sort='updated',
-                                     direction='asc'):
-            pr_dict = pr.as_dict()
-            self._sha_pr_cache.update(project_name, pr_dict)
-            if pr.head.sha != sha:
-                continue
-            if pr_dict in pulls:
-                continue
-            pulls.append(pr_dict)
+        github = self.getGithubClient(project_name, zuul_event_id=event)
+        issues = list(github.search_issues(sha))
 
         log.debug('Got PR on project %s for sha %s', project_name, sha)
-        if len(pulls) > 1:
+        if len(issues) > 1:
             raise Exception('Multiple pulls found with head sha %s' % sha)
 
-        if len(pulls) == 0:
+        if len(issues) == 0:
             return None
-        return pulls.pop()
+
+        pr_body, pr_obj = self.getPull(
+            project_name, issues.pop().issue.number, event)
+        self._sha_pr_cache.update(project_name, pr_body)
+        return pr_body
 
     def getPullReviews(self, pr_obj, project, number, event):
         log = get_annotated_logger(self.log, event)