diff --git a/gitea/pull.go b/gitea/pull.go
index c41ab3b..d653746 100644
--- a/gitea/pull.go
+++ b/gitea/pull.go
@@ -105,6 +105,13 @@ func (c *Client) ListRepoPullRequests(owner, repo string, opt ListPullRequestsOp
 	link, _ := url.Parse(fmt.Sprintf("/repos/%s/%s/pulls", owner, repo))
 	link.RawQuery = opt.QueryEncode()
 	resp, err := c.getParsedResponse("GET", link.String(), jsonHeader, nil, &prs)
+	if c.checkServerVersionGreaterThanOrEqual(version1_14_0) != nil {
+		for i := range prs {
+			if err := fixPullHeadSha(c, prs[i]); err != nil {
+				return prs, resp, err
+			}
+		}
+	}
 	return prs, resp, err
 }
 
@@ -112,6 +119,11 @@ func (c *Client) ListRepoPullRequests(owner, repo string, opt ListPullRequestsOp
 func (c *Client) GetPullRequest(owner, repo string, index int64) (*PullRequest, *Response, error) {
 	pr := new(PullRequest)
 	resp, err := c.getParsedResponse("GET", fmt.Sprintf("/repos/%s/%s/pulls/%d", owner, repo, index), nil, nil, pr)
+	if c.checkServerVersionGreaterThanOrEqual(version1_14_0) != nil {
+		if err := fixPullHeadSha(c, pr); err != nil {
+			return pr, resp, err
+		}
+	}
 	return pr, resp, err
 }
 
@@ -251,3 +263,23 @@ func (c *Client) GetPullRequestPatch(owner, repo string, index int64) ([]byte, *
 func (c *Client) GetPullRequestDiff(owner, repo string, index int64) ([]byte, *Response, error) {
 	return c.getPullRequestDiffOrPatch(owner, repo, "diff", index)
 }
+
+// fixPullHeadSha is a workaround for https://github.com/go-gitea/gitea/issues/12675
+// When no head sha is available, this is because the branch got deleted in the base repo.
+// pr.Head.Ref points in this case not to the head repo branch name, but the base repo ref,
+// which stays available to resolve the commit sha. This is fixed for gitea >= 1.14.0
+func fixPullHeadSha(client *Client, pr *PullRequest) error {
+	if pr.Base != nil && pr.Base.Repository != nil && pr.Base.Repository.Owner != nil &&
+		pr.Head != nil && pr.Head.Ref != "" && pr.Head.Sha == "" {
+		owner := pr.Base.Repository.Owner.UserName
+		repo := pr.Base.Repository.Name
+		refs, _, err := client.GetRepoRefs(owner, repo, pr.Head.Ref)
+		if err != nil {
+			return err
+		} else if len(refs) == 0 {
+			return fmt.Errorf("unable to resolve PR ref '%s'", pr.Head.Ref)
+		}
+		pr.Head.Sha = refs[0].Object.SHA
+	}
+	return nil
+}
diff --git a/gitea/pull_test.go b/gitea/pull_test.go
index a52ddf8..83e325a 100644
--- a/gitea/pull_test.go
+++ b/gitea/pull_test.go
@@ -58,7 +58,7 @@ func TestPull(t *testing.T) {
 
 	diff, _, err := c.GetPullRequestDiff(c.username, repoName, pullUpdateFile.Index)
 	assert.NoError(t, err)
-	assert.Len(t, diff, 1281)
+	assert.True(t, len(diff) > 1100 && len(diff) < 1300)
 	patch, _, err := c.GetPullRequestPatch(c.username, repoName, pullUpdateFile.Index)
 	assert.NoError(t, err)
 	assert.True(t, len(patch) > len(diff))
diff --git a/gitea/repo_test.go b/gitea/repo_test.go
index 3e924a7..e5eedc7 100644
--- a/gitea/repo_test.go
+++ b/gitea/repo_test.go
@@ -138,7 +138,7 @@ func TestGetArchive(t *testing.T) {
 	time.Sleep(time.Second / 2)
 	archive, _, err := c.GetArchive(repo.Owner.UserName, repo.Name, "master", ZipArchive)
 	assert.NoError(t, err)
-	assert.EqualValues(t, 1602, len(archive))
+	assert.True(t, len(archive) > 1500 && len(archive) < 1700)
 }
 
 func TestGetArchiveReader(t *testing.T) {
@@ -153,7 +153,7 @@ func TestGetArchiveReader(t *testing.T) {
 	archive := bytes.NewBuffer(nil)
 	nBytes, err := io.Copy(archive, r)
 	assert.NoError(t, err)
-	assert.EqualValues(t, 1602, nBytes)
+	assert.True(t, nBytes > 1500)
 	assert.EqualValues(t, nBytes, len(archive.Bytes()))
 }