diff --git a/scm-core/src/main/java/sonia/scm/repository/NoCommonHistoryException.java b/scm-core/src/main/java/sonia/scm/repository/NoCommonHistoryException.java
new file mode 100644
index 0000000000..ddb7793d20
--- /dev/null
+++ b/scm-core/src/main/java/sonia/scm/repository/NoCommonHistoryException.java
@@ -0,0 +1,22 @@
+package sonia.scm.repository;
+
+import sonia.scm.BadRequestException;
+
+import static java.util.Collections.emptyList;
+
+@SuppressWarnings("squid:MaximumInheritanceDepth")
+public class NoCommonHistoryException extends BadRequestException {
+
+  public NoCommonHistoryException() {
+    this("no common history");
+  }
+
+  public NoCommonHistoryException(String message) {
+    super(emptyList(), message);
+  }
+
+  @Override
+  public String getCode() {
+    return "4iRct4avG1";
+  }
+}
diff --git a/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/GitUtil.java b/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/GitUtil.java
index 129f723e1c..d726b992ca 100644
--- a/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/GitUtil.java
+++ b/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/GitUtil.java
@@ -62,7 +62,6 @@ import org.eclipse.jgit.util.LfsFactory;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import sonia.scm.ContextEntry;
-import sonia.scm.ScmConstraintViolationException;
 import sonia.scm.util.HttpUtil;
 import sonia.scm.util.Util;
 import sonia.scm.web.GitUserAgentProvider;
@@ -77,7 +76,6 @@ import java.util.concurrent.TimeUnit;
 
 import static java.util.Optional.empty;
 import static java.util.Optional.of;
-import static sonia.scm.ScmConstraintViolationException.Builder.doThrow;
 
 //~--- JDK imports ------------------------------------------------------------
 
@@ -87,7 +85,7 @@ import static sonia.scm.ScmConstraintViolationException.Builder.doThrow;
  */
 public final class GitUtil
 {
-  
+
   private static final GitUserAgentProvider GIT_USER_AGENT_PROVIDER = new GitUserAgentProvider();
 
   /** Field description */
@@ -333,14 +331,14 @@ public final class GitUtil
 
     return branch;
   }
-  
+
   /**
    * Returns {@code true} if the provided reference name is a branch name.
-   * 
+   *
    * @param refName reference name
-   * 
+   *
    * @return {@code true} if the name is a branch name
-   * 
+   *
    * @since 1.50
    */
   public static boolean isBranch(String refName)
@@ -619,11 +617,11 @@ public final class GitUtil
 
   /**
    * Returns the name of the tag or {@code null} if the the ref is not a tag.
-   * 
+   *
    * @param refName ref name
-   * 
+   *
    * @return name of tag or {@link null}
-   * 
+   *
    * @since 1.50
    */
   public static String getTagName(String refName)
@@ -696,7 +694,7 @@ public final class GitUtil
   {
     //J-
     return fs.resolve(dir, DIRECTORY_OBJETCS).exists()
-      && fs.resolve(dir, DIRECTORY_REFS).exists() 
+      && fs.resolve(dir, DIRECTORY_REFS).exists()
       &&!fs.resolve(dir, DIRECTORY_DOTGIT).exists();
     //J+
   }
@@ -736,9 +734,10 @@ public final class GitUtil
       mergeBaseWalk.markStart(mergeBaseWalk.lookupCommit(revision1));
       mergeBaseWalk.markStart(mergeBaseWalk.parseCommit(revision2));
       RevCommit ancestor = mergeBaseWalk.next();
-      doThrow()
-        .violation("revisions " + revision1.name() + " and " + revision2.name() + " are not related and therefore do not have a common ancestor", "revisions")
-        .when(ancestor == null);
+      if (ancestor == null) {
+        String msg = "revisions %s and %s are not related and therefore do not have a common ancestor";
+        throw new NoCommonHistoryException(String.format(msg, revision1.name(), revision2.name()));
+      }
       return ancestor.getId();
     }
   }
diff --git a/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/Differ.java b/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/Differ.java
index ca417550f4..0204ca4e3c 100644
--- a/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/Differ.java
+++ b/scm-plugins/scm-git-plugin/src/main/java/sonia/scm/repository/spi/Differ.java
@@ -55,7 +55,7 @@ final class Differ implements AutoCloseable {
       if (!Strings.isNullOrEmpty(request.getAncestorChangeset()))
       {
         ObjectId otherRevision = repository.resolve(request.getAncestorChangeset());
-        ObjectId ancestorId = computeCommonAncestor(repository, revision, otherRevision);
+        ObjectId ancestorId = GitUtil.computeCommonAncestor(repository, revision, otherRevision);
         RevTree tree = walk.parseCommit(ancestorId).getTree();
         treeWalk.addTree(tree);
       }
@@ -82,10 +82,6 @@ final class Differ implements AutoCloseable {
     return new Differ(commit, walk, treeWalk);
   }
 
-  private static ObjectId computeCommonAncestor(org.eclipse.jgit.lib.Repository repository, ObjectId revision1, ObjectId revision2) throws IOException {
-    return GitUtil.computeCommonAncestor(repository, revision1, revision2);
-  }
-
   private Diff diff() throws IOException {
     List<DiffEntry> entries = DiffEntry.scan(treeWalk);
     return new Diff(commit, entries);
@@ -115,4 +111,5 @@ final class Differ implements AutoCloseable {
       return entries;
     }
   }
+
 }
diff --git a/scm-webapp/src/main/resources/locales/de/plugins.json b/scm-webapp/src/main/resources/locales/de/plugins.json
index b687a7f8ca..41e5737503 100644
--- a/scm-webapp/src/main/resources/locales/de/plugins.json
+++ b/scm-webapp/src/main/resources/locales/de/plugins.json
@@ -176,6 +176,10 @@
       "displayName": "Es wurden keine Änderungen durchgeführt",
       "description": "Das Repository wurde nicht verändert. Daher konnte kein neuer Commit erzeugt werden."
     },
+    "4iRct4avG1": {
+      "displayName": "Die Revisionen haben keinen gemeinsamen Ursprung",
+      "description": "Die Historie der Revisionen hat keinen gemeinsamen Urspung und kann somit auch nicht gegen einen solchen verglichen werden."
+    },
     "65RdZ5atX1": {
       "displayName": "Fehler beim Löschen von Plugin-Dateien",
       "description": "Einige Dateien für die Plugin-Deinstallation konnten nicht gelöscht werden. Dieses kann zu Inkonsistenzen führen, so dass der SCM-Manager nicht mehr korrekt starten kann. Bitte prüfen Sie die Logs und bereinigen Sie das Plugin-Verzeichnis des SCM-Managers manuell. Um die Installation eines Plugins abzubrechen, löschen Sie die zugehörige smp Datei aus dem Plugin-Verzeichnis. Um ein Entfernen eines Plugins zu verhindern, entfernen Sie die Datei namens 'uninstall' aus dem entsprechenden Verzeichnis des Plugins."
diff --git a/scm-webapp/src/main/resources/locales/en/plugins.json b/scm-webapp/src/main/resources/locales/en/plugins.json
index 2e21ffe741..77f8d2f4b9 100644
--- a/scm-webapp/src/main/resources/locales/en/plugins.json
+++ b/scm-webapp/src/main/resources/locales/en/plugins.json
@@ -176,6 +176,10 @@
       "displayName": "No changes were made",
       "description": "No changes were made to the files of the repository. Therefor no new commit could be created."
     },
+    "4iRct4avG1": {
+      "displayName": "The revisions have unrelated histories",
+      "description": "The revisions have unrelated histories. Therefor there is no common commit to compare with."
+    },
     "65RdZ5atX1": {
       "displayName": "Error removing plugin files",
       "description": "Some files to cancel the plugin (un)installation could not be deleted. This can lead to inconsistencies so that the SCM-Manager cannot restart properly. Please check the logs and clean up the plugin folder manually. To cancel the installation of a plugin, remove the corresponding smp file. To cancel the uninstallation, remove the file named 'uninstall' inside the directory for this plugin."