diff --git a/models/migrations/v156.go b/models/migrations/v156.go
index 1e7cf282774b..7158d7bb6b71 100644
--- a/models/migrations/v156.go
+++ b/models/migrations/v156.go
@@ -88,7 +88,7 @@ func fixPublisherIDforTagReleases(x *xorm.Engine) error {
 				repo = new(Repository)
 				has, err := sess.ID(release.RepoID).Get(repo)
 				if err != nil {
-					log.Error("Error whilst loading repository[%d] for release[%d] with tag name %s", release.RepoID, release.ID, release.TagName)
+					log.Error("Error whilst loading repository[%d] for release[%d] with tag name %s. Error: %v", release.RepoID, release.ID, release.TagName, err)
 					return err
 				} else if !has {
 					log.Warn("Release[%d] is orphaned and refers to non-existing repository %d", release.ID, release.RepoID)
@@ -105,13 +105,13 @@ func fixPublisherIDforTagReleases(x *xorm.Engine) error {
 					}
 
 					if _, err := sess.ID(release.RepoID).Get(repo); err != nil {
-						log.Error("Error whilst loading repository[%d] for release[%d] with tag name %s", release.RepoID, release.ID, release.TagName)
+						log.Error("Error whilst loading repository[%d] for release[%d] with tag name %s. Error: %v", release.RepoID, release.ID, release.TagName, err)
 						return err
 					}
 				}
 				gitRepo, err = git.OpenRepository(repoPath(repo.OwnerName, repo.Name))
 				if err != nil {
-					log.Error("Error whilst opening git repo for %-v", repo)
+					log.Error("Error whilst opening git repo for [%d]%s/%s. Error: %v", repo.ID, repo.OwnerName, repo.Name, err)
 					return err
 				}
 			}
@@ -119,18 +119,36 @@ func fixPublisherIDforTagReleases(x *xorm.Engine) error {
 			commit, err := gitRepo.GetTagCommit(release.TagName)
 			if err != nil {
 				if git.IsErrNotExist(err) {
-					log.Warn("Unable to find commit %s for Tag: %s in %-v. Cannot update publisher ID.", err.(git.ErrNotExist).ID, release.TagName, repo)
+					log.Warn("Unable to find commit %s for Tag: %s in [%d]%s/%s. Cannot update publisher ID.", err.(git.ErrNotExist).ID, release.TagName, repo.ID, repo.OwnerName, repo.Name)
 					continue
 				}
-				log.Error("Error whilst getting commit for Tag: %s in %-v.", release.TagName, repo)
+				log.Error("Error whilst getting commit for Tag: %s in [%d]%s/%s. Error: %v", release.TagName, repo.ID, repo.OwnerName, repo.Name, err)
 				return fmt.Errorf("GetTagCommit: %v", err)
 			}
 
+			if commit.Author.Email == "" {
+				log.Warn("Tag: %s in Repo[%d]%s/%s does not have a tagger.", release.TagName, repo.ID, repo.OwnerName, repo.Name)
+				commit, err = gitRepo.GetCommit(commit.ID.String())
+				if err != nil {
+					if git.IsErrNotExist(err) {
+						log.Warn("Unable to find commit %s for Tag: %s in [%d]%s/%s. Cannot update publisher ID.", err.(git.ErrNotExist).ID, release.TagName, repo.ID, repo.OwnerName, repo.Name)
+						continue
+					}
+					log.Error("Error whilst getting commit for Tag: %s in [%d]%s/%s. Error: %v", release.TagName, repo.ID, repo.OwnerName, repo.Name, err)
+					return fmt.Errorf("GetCommit: %v", err)
+				}
+			}
+
+			if commit.Author.Email == "" {
+				log.Warn("Tag: %s in Repo[%d]%s/%s does not have a Tagger and its underlying commit does not have an Author either!", release.TagName, repo.ID, repo.OwnerName, repo.Name)
+				continue
+			}
+
 			if user == nil || !strings.EqualFold(user.Email, commit.Author.Email) {
 				user = new(User)
 				_, err = sess.Where("email=?", commit.Author.Email).Get(user)
 				if err != nil {
-					log.Error("Error whilst getting commit author by email: %s for Tag: %s in %-v.", commit.Author.Email, release.TagName, repo)
+					log.Error("Error whilst getting commit author by email: %s for Tag: %s in [%d]%s/%s. Error: %v", commit.Author.Email, release.TagName, repo.ID, repo.OwnerName, repo.Name, err)
 					return err
 				}
 
@@ -143,7 +161,7 @@ func fixPublisherIDforTagReleases(x *xorm.Engine) error {
 
 			release.PublisherID = user.ID
 			if _, err := sess.ID(release.ID).Cols("publisher_id").Update(release); err != nil {
-				log.Error("Error whilst updating publisher[%d] for release[%d] with tag name %s", release.PublisherID, release.ID, release.TagName)
+				log.Error("Error whilst updating publisher[%d] for release[%d] with tag name %s. Error: %v", release.PublisherID, release.ID, release.TagName, err)
 				return err
 			}
 		}
diff --git a/modules/git/commit_reader.go b/modules/git/commit_reader.go
index a4d15b6bada7..3c1f6f5ffd65 100644
--- a/modules/git/commit_reader.go
+++ b/modules/git/commit_reader.go
@@ -17,7 +17,9 @@ import (
 // If used as part of a cat-file --batch stream you need to limit the reader to the correct size
 func CommitFromReader(gitRepo *Repository, sha SHA1, reader io.Reader) (*Commit, error) {
 	commit := &Commit{
-		ID: sha,
+		ID:        sha,
+		Author:    &Signature{},
+		Committer: &Signature{},
 	}
 
 	payloadSB := new(strings.Builder)
diff --git a/modules/git/tag.go b/modules/git/tag.go
index 0323cc42edd7..23f09e25b6c8 100644
--- a/modules/git/tag.go
+++ b/modules/git/tag.go
@@ -35,6 +35,7 @@ func (tag *Tag) Commit() (*Commit, error) {
 // \n\n separate headers from message
 func parseTagData(data []byte) (*Tag, error) {
 	tag := new(Tag)
+	tag.Tagger = &Signature{}
 	// we now have the contents of the commit object. Let's investigate...
 	nextline := 0
 l: