diff --git a/scm-core/src/main/java/sonia/scm/repository/spi/MergeCommandRequest.java b/scm-core/src/main/java/sonia/scm/repository/spi/MergeCommandRequest.java
index a4e22b5ad1..05f160ec0a 100644
--- a/scm-core/src/main/java/sonia/scm/repository/spi/MergeCommandRequest.java
+++ b/scm-core/src/main/java/sonia/scm/repository/spi/MergeCommandRequest.java
@@ -43,8 +43,7 @@ public class MergeCommandRequest implements Validateable, Resetable, Serializabl
 
   public boolean isValid() {
     return !Strings.isNullOrEmpty(getBranchToMerge())
-      && !Strings.isNullOrEmpty(getTargetBranch())
-      && getAuthor() != null;
+      && !Strings.isNullOrEmpty(getTargetBranch());
   }
 
   public void reset() {
diff --git a/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMergeCommand.java b/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMergeCommand.java
index 50b9636dc2..a060c0fecc 100644
--- a/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMergeCommand.java
+++ b/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMergeCommand.java
@@ -1,5 +1,7 @@
 package sonia.scm.repository.spi;
 
+import org.apache.shiro.SecurityUtils;
+import org.apache.shiro.subject.Subject;
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.MergeResult;
 import org.eclipse.jgit.api.errors.GitAPIException;
@@ -14,6 +16,7 @@ import sonia.scm.repository.InternalRepositoryException;
 import sonia.scm.repository.Person;
 import sonia.scm.repository.api.MergeCommandResult;
 import sonia.scm.repository.api.MergeDryRunCommandResult;
+import sonia.scm.user.User;
 
 import java.io.IOException;
 
@@ -103,9 +106,10 @@ public class GitMergeCommand extends AbstractGitCommand implements MergeCommand
 
     private void doCommit() {
       logger.debug("merged branch {} into {}", toMerge, target);
+      Person authorToUse = determineAuthor();
       try {
         clone.commit()
-          .setAuthor(author.getName(), author.getMail())
+          .setAuthor(authorToUse.getName(), authorToUse.getMail())
           .setMessage(String.format(MERGE_COMMIT_MESSAGE_TEMPLATE, toMerge, target))
           .call();
       } catch (GitAPIException e) {
@@ -113,6 +117,19 @@ public class GitMergeCommand extends AbstractGitCommand implements MergeCommand
       }
     }
 
+    private Person determineAuthor() {
+      if (author == null) {
+        Subject subject = SecurityUtils.getSubject();
+        User user = subject.getPrincipals().oneByType(User.class);
+        String name = user.getDisplayName();
+        String email = user.getMail();
+        logger.debug("no author set; using logged in user: {} <{}>", name, email);
+        return new Person(name, email);
+      } else {
+        return author;
+      }
+    }
+
     private void push() {
       try {
         clone.push().call();
diff --git a/scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitMergeCommandTest.java b/scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitMergeCommandTest.java
index 23b41bf54a..307416011e 100644
--- a/scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitMergeCommandTest.java
+++ b/scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitMergeCommandTest.java
@@ -1,22 +1,32 @@
 package sonia.scm.repository.spi;
 
-import org.assertj.core.api.Assertions;
+import com.github.sdorra.shiro.ShiroRule;
+import com.github.sdorra.shiro.SubjectAware;
+import org.apache.shiro.subject.SimplePrincipalCollection;
+import org.apache.shiro.subject.Subject;
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.lib.PersonIdent;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
+import org.junit.Rule;
 import org.junit.Test;
 import sonia.scm.repository.Person;
 import sonia.scm.repository.api.MergeCommandResult;
+import sonia.scm.user.User;
 
 import java.io.IOException;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-
+@SubjectAware(configuration = "classpath:sonia/scm/configuration/shiro.ini")
 public class GitMergeCommandTest extends AbstractGitCommandTestBase {
 
+  private static final String REALM = "AdminRealm";
+
+  @Rule
+  public ShiroRule shiro = new ShiroRule();
+
   @Test
   public void shouldDetectMergeableBranches() {
     GitMergeCommand command = createCommand();
@@ -73,6 +83,29 @@ public class GitMergeCommandTest extends AbstractGitCommandTestBase {
     assertThat(mergeCommandResult.getFilesWithConflict()).containsExactly("a.txt");
   }
 
+  @Test
+  @SubjectAware(username = "admin", password = "secret")
+  public void shouldTakeAuthorFromSubjectIfNotSet() throws IOException, GitAPIException {
+    shiro.setSubject(
+      new Subject.Builder()
+        .principals(new SimplePrincipalCollection(new User("dirk", "Dirk Gently", "dirk@holistic.det"), REALM))
+        .buildSubject());
+    GitMergeCommand command = createCommand();
+    MergeCommandRequest request = new MergeCommandRequest();
+    request.setTargetBranch("master");
+    request.setBranchToMerge("mergeable");
+
+    MergeCommandResult mergeCommandResult = command.merge(request);
+
+    assertThat(mergeCommandResult.isSuccess()).isTrue();
+
+    Repository repository = createContext().open();
+    Iterable<RevCommit> mergeCommit = new Git(repository).log().add(repository.resolve("master")).setMaxCount(1).call();
+    PersonIdent mergeAuthor = mergeCommit.iterator().next().getAuthorIdent();
+    assertThat(mergeAuthor.getName()).isEqualTo("Dirk Gently");
+    assertThat(mergeAuthor.getEmailAddress()).isEqualTo("dirk@holistic.det");
+  }
+
   private GitMergeCommand createCommand() {
     return new GitMergeCommand(createContext(), repository, new SimpleGitWorkdirFactory());
   }