diff --git a/gradle/changelog/master_on_initial_mirror.yaml b/gradle/changelog/master_on_initial_mirror.yaml
new file mode 100644
index 0000000000..d5572ba76f
--- /dev/null
+++ b/gradle/changelog/master_on_initial_mirror.yaml
@@ -0,0 +1,2 @@
+- type: fixed
+  description: Handle rejected master branch on initial mirror synchronization correctly ([#1747](https://github.com/scm-manager/scm-manager/pull/1747))
diff --git a/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMirrorCommand.java b/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMirrorCommand.java
index c785d72c23..a1825d5412 100644
--- a/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMirrorCommand.java
+++ b/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/GitMirrorCommand.java
@@ -74,6 +74,7 @@ import static java.util.Collections.unmodifiableMap;
 import static java.util.Optional.empty;
 import static java.util.Optional.of;
 import static org.eclipse.jgit.lib.RefUpdate.Result.NEW;
+import static org.eclipse.jgit.lib.RefUpdate.Result.REJECTED_CURRENT_BRANCH;
 import static sonia.scm.repository.api.MirrorCommandResult.ResultType.FAILED;
 import static sonia.scm.repository.api.MirrorCommandResult.ResultType.OK;
 import static sonia.scm.repository.api.MirrorCommandResult.ResultType.REJECTED_UPDATES;
@@ -135,6 +136,18 @@ public class GitMirrorCommand extends AbstractGitCommand implements MirrorComman
 
     private ResultType result = OK;
 
+    /**
+     * On the first synchronization, the clone has the implicit branch "master". This cannot be
+     * changed in JGit. When we fetch the refs from the repository that should be mirrored, the
+     * master branch of the clone will be updated to the revision of the remote repository (if
+     * it has a master branch). If now the master branch shall be filtered from mirroring (ie.
+     * if it is rejected), we normally would delete the ref in this clone. But because it is
+     * the current branch, it cannot be deleted. We detect this, set this variable to
+     * {@code true}, and later, after we have pushed the result, delete the master branch by
+     * pushing an empty ref to the central repository.
+     */
+    private boolean deleteMasterAfterInitialSync = false;
+
     private Worker(GitContext context, MirrorCommandRequest mirrorCommandRequest, sonia.scm.repository.Repository repository, Git git) {
       super(git, context, repository);
       this.mirrorCommandRequest = mirrorCommandRequest;
@@ -167,9 +180,16 @@ public class GitMirrorCommand extends AbstractGitCommand implements MirrorComman
       }
 
       push(generatePushRefSpecs().toArray(new String[0]));
+      cleanUpMasterIfNecessary();
       return new MirrorCommandResult(result, mirrorLog, stopwatch.stop().elapsed());
     }
 
+    private void cleanUpMasterIfNecessary() {
+      if (deleteMasterAfterInitialSync) {
+        push(":refs/heads/master");
+      }
+    }
+
     private Collection<String> generatePushRefSpecs() {
       Collection<String> refSpecs = new ArrayList<>();
       refSpecs.add("refs/heads/*:refs/heads/*");
@@ -302,7 +322,10 @@ public class GitMirrorCommand extends AbstractGitCommand implements MirrorComman
       private void deleteReference(String targetRef) throws IOException {
         RefUpdate deleteUpdate = git.getRepository().getRefDatabase().newUpdate(targetRef, true);
         deleteUpdate.setForceUpdate(true);
-        deleteUpdate.delete();
+        RefUpdate.Result deleteResult = deleteUpdate.delete();
+        if (deleteResult == REJECTED_CURRENT_BRANCH) {
+          deleteMasterAfterInitialSync = true;
+        }
       }
 
       private boolean isDeletedReference(TrackingRefUpdate ref) {
diff --git a/scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitMirrorCommandTest.java b/scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitMirrorCommandTest.java
index a5474add54..4c591c85f7 100644
--- a/scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitMirrorCommandTest.java
+++ b/scm-plugins/scm-git-plugin/src/test/java/sonia/scm/repository/spi/GitMirrorCommandTest.java
@@ -112,6 +112,36 @@ public class GitMirrorCommandTest extends AbstractGitCommandTestBase {
     }
   }
 
+  @Test
+  public void shouldFilterMasterBranchWhenFilteredOnInitialMirror() throws IOException, GitAPIException {
+    MirrorCommandResult result = callMirrorCommand(repositoryDirectory.getAbsolutePath(), c -> {
+      c.setFilter(new MirrorFilter() {
+        @Override
+        public Filter getFilter(FilterContext context) {
+          return new Filter() {
+            @Override
+            public Result acceptBranch(BranchUpdate branch) {
+              if (branch.getBranchName().equals("master")) {
+                return Result.reject("master not accepted");
+              } else {
+                return Result.accept();
+              }
+            }
+          };
+        }
+      });
+    });
+
+    assertThat(result.getResult()).isEqualTo(REJECTED_UPDATES);
+    assertThat(result.getLog())
+      .contains("- 000000000..fcd0ef183 master (master not accepted)");
+
+    try (Git createdMirror = Git.open(clone)) {
+      assertThat(createdMirror.branchList().call().stream().filter(r -> r.getName().contains("master")).findAny())
+        .isEmpty();
+    }
+  }
+
   @Test
   public void shouldCreateEmptyLogWhenNoChangesFound() {
     callMirrorCommand();