diff --git a/src/main/java/org/kohsuke/github/GHRepository.java b/src/main/java/org/kohsuke/github/GHRepository.java
index e444fe4657..917be54d7f 100644
--- a/src/main/java/org/kohsuke/github/GHRepository.java
+++ b/src/main/java/org/kohsuke/github/GHRepository.java
@@ -690,7 +690,23 @@ public GHCompare getCompare(GHCommit id1, GHCommit id2) throws IOException {
     }
 
     public GHCompare getCompare(GHBranch id1, GHBranch id2) throws IOException {
-        return getCompare(id1.getName(),id2.getName());
+
+        GHRepository owner1 = id1.getOwner();
+        GHRepository owner2 = id2.getOwner();
+
+        // If the owner of the branches is different, we have a cross-fork compare.
+        if (owner1!=null && owner2!=null) {
+            String ownerName1 = owner1.getOwnerName();
+            String ownerName2 = owner2.getOwnerName();
+            if (!StringUtils.equals(ownerName1, ownerName2)) {
+                String qualifiedName1 = String.format("%s:%s", ownerName1, id1.getName());
+                String qualifiedName2 = String.format("%s:%s", ownerName2, id2.getName());
+                return getCompare(qualifiedName1, qualifiedName2);
+            }
+        }
+
+        return getCompare(id1.getName(), id2.getName());
+
     }
 
     /**