diff --git a/src/model.ts b/src/model.ts
index 926bf40db..61eb42b76 100644
--- a/src/model.ts
+++ b/src/model.ts
@@ -857,15 +857,31 @@ export class GitExtension implements IGitExtension {
    * @throws {Git.GitResponseError} If the server response is not ok
    * @throws {ServerConnection.NetworkError} If the request cannot be made
    */
-  async showPrefix(path: string): Promise<Git.IShowPrefixResult> {
-    return await this._taskHandler.execute<Git.IShowPrefixResult>(
-      'git:fetch:prefix_path',
-      async () => {
-        return await requestAPI<Git.IShowPrefixResult>('show_prefix', 'POST', {
-          current_path: path
-        });
+  async showPrefix(path: string): Promise<string | null> {
+    try {
+      const data = await this._taskHandler.execute<Git.IShowPrefixResult>(
+        'git:fetch:prefix_path',
+        async () => {
+          return await requestAPI<Git.IShowPrefixResult>(
+            'show_prefix',
+            'POST',
+            {
+              current_path: path
+            }
+          );
+        }
+      );
+      return data.under_repo_path || null;
+    } catch (error) {
+      if (
+        error instanceof Git.GitResponseError &&
+        error.response.status === 500 &&
+        error.json.code === 128
+      ) {
+        return null;
       }
-    );
+      throw error;
+    }
   }
 
   /**
diff --git a/src/tokens.ts b/src/tokens.ts
index 8ef0a2081..def8d9068 100644
--- a/src/tokens.ts
+++ b/src/tokens.ts
@@ -383,7 +383,7 @@ export interface IGitExtension extends IDisposable {
    * @throws {Git.GitResponseError} If the server response is not ok
    * @throws {ServerConnection.NetworkError} If the request cannot be made
    */
-  showPrefix(path: string): Promise<Git.IShowPrefixResult>;
+  showPrefix(path: string): Promise<string | null>;
 
   /**
    * Get the top level path of repository 'path'
diff --git a/tests/model.spec.tsx b/tests/model.spec.tsx
index 6545c564f..27cbe302e 100644
--- a/tests/model.spec.tsx
+++ b/tests/model.spec.tsx
@@ -119,6 +119,44 @@ describe('IGitExtension', () => {
     });
   });
 
+  describe('#showPrefix', () => {
+    it('should return a string if the folder is a git repository', async () => {
+      const fakeRepo = '/repo';
+      mockResponses['show_prefix'] = {
+        body: () => {
+          return { code: 0, under_repo_path: fakeRepo };
+        }
+      };
+      const topLevel = await model.showPrefix('/repo/cwd');
+      expect(topLevel).toEqual(fakeRepo);
+    });
+
+    it('should return null if the repository is not a git repository', async () => {
+      mockResponses['show_prefix'] = {
+        body: () => {
+          return { code: 128 };
+        },
+        status: 500
+      };
+      const topLevel = await model.showPrefix('/repo/cwd');
+      expect(topLevel).toBeNull();
+    });
+
+    it('should throw an exception if the server otherwise', async () => {
+      mockResponses['show_prefix'] = {
+        body: () => {
+          return { code: 128 };
+        },
+        status: 401
+      };
+      try {
+        await model.showPrefix('/repo/cwd');
+      } catch (error) {
+        expect(error).toBeInstanceOf(Git.GitResponseError);
+      }
+    });
+  });
+
   describe('#showTopLevel', () => {
     it('should return a string if the folder is a git repository', async () => {
       const fakeRepo = '/path/to/repo';