diff --git a/release-notes/8.0.0/fix/3935.md b/release-notes/8.0.0/fix/3935.md
new file mode 100644
index 0000000000..73ba10a6dc
--- /dev/null
+++ b/release-notes/8.0.0/fix/3935.md
@@ -0,0 +1 @@
+- Fixed an issue where migrated activities (such as reviews) were mapped to the user who initiated the migration rather than the Ghost user, if the external user could not be mapped to a local one. This mapping mismatch led to internal server errors in some cases (forgejo/forgejo#3860).
diff --git a/services/migrations/gitea_uploader.go b/services/migrations/gitea_uploader.go
index 4d54de0b07..3ba4ca203b 100644
--- a/services/migrations/gitea_uploader.go
+++ b/services/migrations/gitea_uploader.go
@@ -996,7 +996,7 @@ func (g *GiteaLocalUploader) remapUser(source user_model.ExternalUserMigrated, t
 	if userID > 0 {
 		return target.RemapExternalUser("", 0, userID)
 	}
-	return target.RemapExternalUser(source.GetExternalName(), source.GetExternalID(), g.doer.ID)
+	return target.RemapExternalUser(source.GetExternalName(), source.GetExternalID(), user_model.GhostUserID)
 }
 
 func (g *GiteaLocalUploader) remapLocalUser(source user_model.ExternalUserMigrated) (int64, error) {
diff --git a/services/migrations/gitea_uploader_test.go b/services/migrations/gitea_uploader_test.go
index e98582f31a..35da8290c8 100644
--- a/services/migrations/gitea_uploader_test.go
+++ b/services/migrations/gitea_uploader_test.go
@@ -145,24 +145,24 @@ func TestGiteaUploadRemapLocalUser(t *testing.T) {
 
 	//
 	// The externalID does not match any existing user, everything
-	// belongs to the doer
+	// belongs to the Ghost user
 	//
 	target := repo_model.Release{}
 	uploader.userMap = make(map[int64]int64)
 	err := uploader.remapUser(&source, &target)
 	assert.NoError(t, err)
-	assert.EqualValues(t, doer.ID, target.GetUserID())
+	assert.EqualValues(t, user_model.GhostUserID, target.GetUserID())
 
 	//
 	// The externalID matches a known user but the name does not match,
-	// everything belongs to the doer
+	// everything belongs to the Ghost user
 	//
 	source.PublisherID = user.ID
 	target = repo_model.Release{}
 	uploader.userMap = make(map[int64]int64)
 	err = uploader.remapUser(&source, &target)
 	assert.NoError(t, err)
-	assert.EqualValues(t, doer.ID, target.GetUserID())
+	assert.EqualValues(t, user_model.GhostUserID, target.GetUserID())
 
 	//
 	// The externalID and externalName match an existing user, everything
@@ -195,13 +195,13 @@ func TestGiteaUploadRemapExternalUser(t *testing.T) {
 
 	//
 	// When there is no user linked to the external ID, the migrated data is authored
-	// by the doer
+	// by the Ghost user
 	//
 	uploader.userMap = make(map[int64]int64)
 	target := repo_model.Release{}
 	err := uploader.remapUser(&source, &target)
 	assert.NoError(t, err)
-	assert.EqualValues(t, doer.ID, target.GetUserID())
+	assert.EqualValues(t, user_model.GhostUserID, target.GetUserID())
 
 	//
 	// Link the external ID to an existing user