diff --git a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/server/Oauth2Filter.java b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/server/Oauth2Filter.java
index dfcfdf21be..bfbf0d6eea 100644
--- a/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/server/Oauth2Filter.java
+++ b/services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/server/Oauth2Filter.java
@@ -40,6 +40,18 @@ public class Oauth2Filter implements Filter {
     @Override
     public void init(FilterConfig filterConfig) {}
 
+    private void sendResponse(ServletResponse servletResponse, int code, List<String> lines) throws IOException {
+        HttpServletResponse response = ((HttpServletResponse) servletResponse);
+        response.setContentType("text/plain");
+        response.setStatus(code);
+        PrintWriter w = response.getWriter();
+        for (String line : lines) {
+            w.println(line);
+        }
+        w.close();
+        return;
+    }
+
     /**
      * The original request from git will not contain the Authorization header.
      *
@@ -57,8 +69,16 @@ public class Oauth2Filter implements Filter {
             ServletResponse servletResponse,
             FilterChain filterChain
     ) throws IOException, ServletException {
+        String requestUri = ((Request) servletRequest).getRequestURI();
+        if (requestUri.startsWith("/project")) {
+            Log.info("[{}] Invalid request URI", requestUri);
+            sendResponse(servletResponse,400, Arrays.asList(
+                    "Invalid Project ID (must not have a '/project' prefix)"
+            ));
+            return;
+        }
         String project = Util.removeAllSuffixes(
-                ((Request) servletRequest).getRequestURI().split("/")[1],
+                requestUri.split("/")[1],
                 ".git"
         );
         // Reject v1 ids, the request will be rejected by v1 anyway
diff --git a/services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/application/WLGitBridgeIntegrationTest.java b/services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/application/WLGitBridgeIntegrationTest.java
index b45b27be7a..f150585f0f 100644
--- a/services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/application/WLGitBridgeIntegrationTest.java
+++ b/services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/application/WLGitBridgeIntegrationTest.java
@@ -865,6 +865,32 @@ public class WLGitBridgeIntegrationTest {
         wlgb.stop();
     }
 
+    @Test
+    public void cannotCloneProjectWithSlash() throws IOException, GitAPIException, InterruptedException {
+        int gitBridgePort = 33886;
+        int mockServerPort = 3886;
+
+        MockSnapshotServer server = new MockSnapshotServer(mockServerPort, getResource("/canCloneARepository").toFile());
+        server.start();
+        server.setState(states.get("canCloneARepository").get("state"));
+        GitBridgeApp wlgb = new GitBridgeApp(new String[] {
+                makeConfigFile(gitBridgePort, mockServerPort)
+        });
+
+        wlgb.run();
+        Process gitProcess = runtime.exec("git clone http://127.0.0.1:" + gitBridgePort + "/project/1234abcd", null, dir);
+        assertNotEquals(0, gitProcess.waitFor());
+
+        List<String> actual = Util.linesFromStream(gitProcess.getErrorStream(), 0, "");
+        assertEquals(Arrays.asList(
+            "Cloning into '1234abcd'...",
+            "remote: Invalid Project ID (must not have a '/project' prefix)",
+            "fatal: unable to access 'http://127.0.0.1:33886/project/1234abcd/': The requested URL returned error: 400"
+        ), actual);
+
+        wlgb.stop();
+    }
+
     private String makeConfigFile(
             int port,
             int apiPort