diff --git a/bots/pr/src/main/java/org/openjdk/skara/bots/pr/CheckRun.java b/bots/pr/src/main/java/org/openjdk/skara/bots/pr/CheckRun.java
index 8031721b5..25cedd7b7 100644
--- a/bots/pr/src/main/java/org/openjdk/skara/bots/pr/CheckRun.java
+++ b/bots/pr/src/main/java/org/openjdk/skara/bots/pr/CheckRun.java
@@ -549,7 +549,7 @@ private String reviewUsingSkaraHelp() {
     }
 
     private String reviewUsingDiffsHelp() {
-        var diffUrl = pr.repository().webUrl() + "/pull/" + pr.id() + ".diff";
+        var diffUrl = pr.repository().diffUrl(pr.id());
         return "Download this PR as a diff file: \\\n" +
                 "<a href=\"" + diffUrl + "\">" + diffUrl + "</a>\n";
     }
diff --git a/bots/tester/src/test/java/org/openjdk/skara/bots/tester/InMemoryHostedRepository.java b/bots/tester/src/test/java/org/openjdk/skara/bots/tester/InMemoryHostedRepository.java
index 87e06ad65..9621bfed4 100644
--- a/bots/tester/src/test/java/org/openjdk/skara/bots/tester/InMemoryHostedRepository.java
+++ b/bots/tester/src/test/java/org/openjdk/skara/bots/tester/InMemoryHostedRepository.java
@@ -108,6 +108,11 @@ public URI webUrl(String baseRef, String headRef) {
         return null;
     }
 
+    @Override
+    public URI diffUrl(String prId) {
+        return webUrl();
+    }
+
     @Override
     public VCS repositoryType() {
         return null;
diff --git a/forge/src/main/java/org/openjdk/skara/forge/HostedRepository.java b/forge/src/main/java/org/openjdk/skara/forge/HostedRepository.java
index 95c42e9ff..c36e6cec6 100644
--- a/forge/src/main/java/org/openjdk/skara/forge/HostedRepository.java
+++ b/forge/src/main/java/org/openjdk/skara/forge/HostedRepository.java
@@ -64,6 +64,7 @@ PullRequest createPullRequest(HostedRepository target,
     URI webUrl(Branch branch);
     URI webUrl(Tag tag);
     URI webUrl(String baseRef, String headRef);
+    URI diffUrl(String prId);
     VCS repositoryType();
     String fileContents(String filename, String ref);
     String namespace();
diff --git a/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java b/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java
index e7b02481e..5052f1a57 100644
--- a/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java
+++ b/forge/src/main/java/org/openjdk/skara/forge/github/GitHubRepository.java
@@ -218,6 +218,12 @@ public URI webUrl(String baseRef, String headRef) {
         return gitHubHost.getWebURI(endpoint);
     }
 
+    @Override
+    public URI diffUrl(String prId) {
+        var endpoint = "/" + repository + "/pull/" + prId + ".diff";
+        return gitHubHost.getWebURI(endpoint);
+    }
+
     @Override
     public VCS repositoryType() {
         return VCS.GIT;
diff --git a/forge/src/main/java/org/openjdk/skara/forge/gitlab/GitLabRepository.java b/forge/src/main/java/org/openjdk/skara/forge/gitlab/GitLabRepository.java
index d1c93d14b..fc04628e3 100644
--- a/forge/src/main/java/org/openjdk/skara/forge/gitlab/GitLabRepository.java
+++ b/forge/src/main/java/org/openjdk/skara/forge/gitlab/GitLabRepository.java
@@ -210,6 +210,15 @@ public URI webUrl(String baseRef, String headRef) {
                          .build();
     }
 
+    @Override
+    public URI diffUrl(String prId) {
+        // GitLab is too smart for it's own best and mangles URLs that contain a
+        // partial hit with the base MR, hence the double slash.
+        return URIBuilder.base(gitLabHost.getUri())
+                .setPath("/" + projectName + "/-/merge_requests//" + prId + ".diff")
+                .build();
+    }
+
     @Override
     public VCS repositoryType() {
         return VCS.GIT;
diff --git a/test/src/main/java/org/openjdk/skara/test/TestHostedRepository.java b/test/src/main/java/org/openjdk/skara/test/TestHostedRepository.java
index ffa60cd48..d6e93f85a 100644
--- a/test/src/main/java/org/openjdk/skara/test/TestHostedRepository.java
+++ b/test/src/main/java/org/openjdk/skara/test/TestHostedRepository.java
@@ -146,6 +146,11 @@ public URI webUrl(String baseRef, String headRef) {
         return URI.create(url().toString() + "/" + baseRef + "..." + headRef);
     }
 
+    @Override
+    public URI diffUrl(String prId) {
+        return webUrl();
+    }
+
     @Override
     public VCS repositoryType() {
         return VCS.GIT;