diff --git a/src/GitHub.App/Services/PullRequestEditorService.cs b/src/GitHub.App/Services/PullRequestEditorService.cs
index 597519f7ca..1ab40754ec 100644
--- a/src/GitHub.App/Services/PullRequestEditorService.cs
+++ b/src/GitHub.App/Services/PullRequestEditorService.cs
@@ -119,7 +119,8 @@ public async Task<ITextView> OpenFile(
 
                     if (!workingDirectory)
                     {
-                        AddBufferTag(wpfTextView.TextBuffer, session, fullPath, commitSha, null);
+                        var gitPath = ToGitPath(session.LocalRepository, fullPath);
+                        AddBufferTag(wpfTextView.TextBuffer, session, gitPath, commitSha, null);
                         EnableNavigateToEditor(textView, session);
                     }
                 }
@@ -485,6 +486,17 @@ static string GetAbsolutePath(LocalRepositoryModel localRepository, string relat
             return Path.Combine(localPath, relativePath);
         }
 
+        static string ToGitPath(LocalRepositoryModel localRepository, string path)
+        {
+            var basePath = localRepository.LocalPath + Path.DirectorySeparatorChar;
+            if (path.StartsWith(basePath, StringComparison.OrdinalIgnoreCase))
+            {
+                return path.Substring(basePath.Length).Replace(Path.DirectorySeparatorChar, '/');
+            }
+
+            throw new ArgumentException($"Path '{path}' is not in the working directory '{localRepository.LocalPath}'");
+        }
+
         string GetText(IVsTextView textView)
         {
             IVsTextLines buffer;
@@ -561,13 +573,15 @@ void ShowErrorInStatusBar(string message, Exception e)
         void AddBufferTag(
             ITextBuffer buffer,
             IPullRequestSession session,
-            string path,
+            string gitPath,
             string commitSha,
             DiffSide? side)
         {
+            Guard.ArgumentIsGitPath(gitPath, nameof(gitPath));
+
             buffer.Properties.GetOrCreateSingletonProperty(
                 typeof(PullRequestTextBufferInfo),
-                () => new PullRequestTextBufferInfo(session, path, commitSha, side));
+                () => new PullRequestTextBufferInfo(session, gitPath, commitSha, side));
 
             var projection = buffer as IProjectionBuffer;
 
@@ -575,7 +589,7 @@ void AddBufferTag(
             {
                 foreach (var source in projection.SourceBuffers)
                 {
-                    AddBufferTag(source, session, path, commitSha, side);
+                    AddBufferTag(source, session, gitPath, commitSha, side);
                 }
             }
         }
diff --git a/src/GitHub.InlineReviews/Services/PullRequestSession.cs b/src/GitHub.InlineReviews/Services/PullRequestSession.cs
index 783254237e..284f7cd37c 100644
--- a/src/GitHub.InlineReviews/Services/PullRequestSession.cs
+++ b/src/GitHub.InlineReviews/Services/PullRequestSession.cs
@@ -110,22 +110,6 @@ public async Task<string> GetMergeBase()
             return mergeBase;
         }
 
-        /// <inheritdoc/>
-        public string GetRelativePath(string path)
-        {
-            if (Path.IsPathRooted(path))
-            {
-                var basePath = LocalRepository.LocalPath;
-
-                if (path.StartsWith(basePath, StringComparison.OrdinalIgnoreCase) && path.Length > basePath.Length + 1)
-                {
-                    return path.Substring(basePath.Length + 1);
-                }
-            }
-
-            return null;
-        }
-
         /// <inheritdoc/>
         public async Task PostReviewComment(
             string body,